[PATCH v2] powerpc: Update compilation flags with core specific options

[Udma Catalin-Dan-B32721]

> > The assembler option is redundant if the -mcpu= flag is set.
> > The patch fixes the kernel compilation problem for e5500/e6500
> > when using gcc option -mcpu=e5500/e6500.
> >
> > Signed-off-by: Catalin Udma <catalin.udma at freescale.com>
> > ---
> > changes for v2:
> >    - update also KBUILD_AFLAGS with -mcpu and -msoft-float flags
> >
> > arch/powerpc/Makefile |   16 +++++++++++++++-
> > 1 files changed, 15 insertions(+), 1 deletions(-)
> 
> Is the assembler redundant for older toolchains?
> 
> - k
[CU] gcc defines the mapping from -mcpu to assembler options in file
gcc/config/rs6000/rs6000.h, like this:
	%{mcpu=8540: -me500} \
	%{mcpu=8548: -me500} \
	%{mcpu=e300c2: -me300} \
	%{mcpu=e300c3: -me300} \
	%{mcpu=e500mc: -me500mc} \
	%{mcpu=e500mc64: -me500mc64} \
	%{mcpu=e5500: -me5500} \
	%{mcpu=e6500: -me6500} \

I have checked this mapping from gcc 3.3 (where 8540 entry was added) to
3.4, 4.3, 4.4 and 4.8.1...The -Wa option is redundant for all these
older toolchains.
Catalin