[ppc] ASFLAGS

[Hollis Blanchard]

I'm noticing that COMMON_ASFLAGS in conf/powerpc-ieee1275.rmk is never 
used (in the .mk file). crt0.S is compiled using CFLAGS just like all 
the .c files. genmk.rb seems to have code to account for .c vs .S, but 
it's not working.

It currently reads like this:
        COMMON_ASFLAGS = -nostdinc -fno-builtin -D__ASSEMBLY__

The first two flags are inappropriate for assembly files, and nothing 
uses __ASSEMBLY__ at all... Should COMMON_ASFLAGS be removed entirely?

-Hollis