sh: Conditionalize gUSA support.

This conditionalizes gUSA support. gUSA is not supported on
SMP configurations, and it's not necessary there anyways due
to having other atomicity options (ie, movli.l/movco.l).

Anything implementing the LL/SC semantics (all SH-4A CPUs)
can switch to userspace atomicity implementations without
requiring gUSA. This is left default-enabled on all UP so
that glibc doesn't break.

Those that know what they are doing can disable this explicitly.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
index b467280..e0317ed 100644
--- a/arch/sh/kernel/entry-common.S
+++ b/arch/sh/kernel/entry-common.S
@@ -176,7 +176,7 @@
 	jmp	@r1
 	 lds	r0, pr
 work_resched:
-#ifndef CONFIG_PREEMPT
+#if defined(CONFIG_GUSA) && !defined(CONFIG_PREEMPT)
 	! gUSA handling
 	mov.l	@(OFF_SP,r15), r0	! get user space stack pointer
 	mov	r0, r1