powerpc/8xx: Remove specific code from fast_exception_return

powerpc/8xx: Remove specific code from fast_exception_return

The label 2: in fast_exception_return is a leftover from
commit b96bae3ae2cb ("powerpc/32: Replace ASM exception exit by C
exception exit from ppc64"). Once removed, we see that
fast_exception_return is a standalone function that is called only
from pieces of assembly dedicated to book3s/32 or booke, never by
common code or 8xx code.

So remove the clear of MSR[RI] enclosed in #ifdef CONFIG_PPC_8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/39de3e0f0122b571474b1ba352a2dc3ad8cb71dd.1756304318.git.christophe.leroy@csgroup.eu