Revert "uboot-mediatek: fix build on Mac OS X"

This reverts commit 997ff74.
78cbd5apick as it should be fixed in commit 78cbd5a ("tools: macOS:
types.h: fix missing unsigned types").

References: openwrt#13833
Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit f691830)