greenhills support: Fix ?? "trigraphs not allowed" warnings

[extinguish]

Summary

fix the ?? "trigraphs not allowed" build warnings with greenhills compiler
the detailed build warning are:

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 263: warning #1695-D:
          trigraphs not allowed
  #define  PCI_PM_CTRL_DATA_SEL_MASK        0x1e00  /* Data select (??) */
                                                                    ^

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 264: warning #1695-D:
          trigraphs not allowed
  #define  PCI_PM_CTRL_DATA_SCALE_MASK      0x6000  /* Data scale (??) */
                                                                   ^

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 266: warning #1695-D:
          trigraphs not allowed
  #define PCI_PM_PPB_EXTENSIONS             6       /* PPB support extensions (??) */
                                                                               ^

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 267: warning #1695-D:
          trigraphs not allowed
  #define  PCI_PM_PPB_B2_B3                 0x40    /* Stop clock when in D3hot (??) */
                                                                                 ^

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 268: warning #1695-D:
          trigraphs not allowed
  #define  PCI_PM_BPCC_ENABLE               0x80    /* Bus power/clock control enable (??) */
                                                                                       ^

"/mnt/yang/qixinwei_vela_warnings_04_23/nuttx/include/nuttx/pci/pci_regs.h", line 269: warning #1695-D:
          trigraphs not allowed
  #define PCI_PM_DATA_REGISTER              7       /* (??) */

Impact

has no impact on current implementation

Testing

1. has pass the ostest
2. has tested on ghs and gcc compiler

[nuttxpr]

[Experimental Bot, please feedback here]

NuttX PR Review

Meets Requirements? Partially

Summary:
While the summary explains the "why" (fixing build warnings) and "what" (trigraph issue), it lacks details on "how" the change was implemented.

Impact:
The PR claims no user, build, hardware, or compatibility impact. This seems reasonable for a trigraph fix. However, clarifying if documentation or security is impacted is recommended.

Testing:

• Insufficient Detail: Listing OS, compiler versions, specific architectures (not just "ghs and gcc"), and board configurations is crucial for reproducibility.
• Missing Logs: The "before" and "after" logs are essential to demonstrate the warning's presence and its successful resolution.

Recommendations:

1. Expand Summary: Briefly describe the technical approach to resolving the trigraph issue (e.g., "Replaced trigraphs with their equivalent C++ characters").
2. Complete Impact Assessment: Address the potential impact on documentation and security, even if it's "NO" with a brief justification.
3. Provide Specific Testing Details:
   • List the exact build host OS, versions of GCC and the Green Hills compiler, and target architectures/boards used.
   • Include the relevant snippets of the build logs demonstrating the warnings before the change and their absence after.

Overall: The PR addresses a valid issue, but needs more details for thorough review and merging.