x86/raid6: correctly check for assembler capabilities

Just like for AVX2 (which simply needs an #if -> #ifdef conversion),
SSSE3 assembler support should be checked for before using it.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --cc arch/x86/Makefile
Simple merge

diff --cc lib/raid6/algos.c
Simple merge

diff --cc lib/raid6/recov_avx2.c
Simple merge

diff --cc lib/raid6/recov_ssse3.c
Simple merge