MIPS: Guard some macros with __ASSEMBLY__ in asm.h

MIPS: Guard some macros with __ASSEMBLY__ in asm.h

There are some assembly macros with very generic naming
being defined asm.h. They are clashing with other macros
from C code.

Guard them with __ASSEMBLY__ to prevent futher clashes.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/linux-mips/8d78894-dd89-9f4d-52bb-1b873c50be9c@linux-m68k.org/
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>