sparc32: Add -Av8 to assembler command line.

Newer version of binutils are more strict about specifying the
correct options to enable certain classes of instructions.

The sparc32 build is done for v7 in order to support sun4c systems
which lack hardware integer multiply and divide instructions.

So we have to pass -Av8 when building the assembler routines that
use these instructions and get patched into the kernel when we find
out that we have a v8 capable cpu.

Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>