sh: Don't include fault-nommu on SH-2/SH-2A.

fault-nommu defines the page fault handler stubs for SH-3/4 parts,
but is not needed on SH-2/SH-2A now that the entry code has been
logically separated.

Add it in for SH-3 and SH-4 explicitly.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>