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/signal.c b/arch/sh/kernel/signal.c
index 0f657d3..2f42442 100644
--- a/arch/sh/kernel/signal.c
+++ b/arch/sh/kernel/signal.c
@@ -507,6 +507,7 @@
 						ctrl_inw(regs->pc - 4));
 				break;
 		}
+#ifdef CONFIG_GUSA
 	} else {
 		/* gUSA handling */
 		preempt_disable();
@@ -523,6 +524,7 @@
 		}
 
 		preempt_enable_no_resched();
+#endif
 	}
 
 	/* Set up the stack frame */