These lines originate in Linux;  it looks like Linux folks chose to
hide bunch of warnings reported by clang rather than fixing C code.

In U-boot, warnings are being fixed thanks to Jeroen's great efforts.
Let's stop suppressing clang warnings.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Jeroen Hofstee <jeroen@myspectrum.nl>