powerpc/32: Remove FIX_SRR1

FIX_SRR1() is defined as blank. Last useful instance of FIX_SRR1()
was removed by commit 40ef8cbc ("powerpc: Get 64-bit configs to
compile with ARCH=powerpc") in 2005.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <oss@buserror.net>