build_bug.h

As commit 84b8bf6d ("bug.h: move BUILD_BUG_* defines to
include/linux/bug.h") noted, include/linux/bug.h was locally
modified for U-Boot because the name conflict of error() caused
build errors at that time.

Now error() is gone, so we can fully sync BUILD_BUG* with Linux.
These macros are just compile-time utilities.  Nothing depends on
platform code, so it should make sense to simply copy Linux's ones.

Please note Linux split BUILD_BUG stuff out into <linux/build_bug.h>
by commit bc6245e5efd7.  Let's follow it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>