sh: Need IRQs enabled for init_fpu().

This tosses in a local_irq_enable()/disable() pair around the init_fpu()
callsite in the FPU state restore exception handler. Fixes up a slab BUG
triggered by making a slab cache allocation that can sleep whilst
irqs_disabled(). This follows the behaviour undertaken by the x86
implementation.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/kernel/cpu/fpu.c b/arch/sh/kernel/cpu/fpu.c
index c23e672..f059ed6 100644
--- a/arch/sh/kernel/cpu/fpu.c
+++ b/arch/sh/kernel/cpu/fpu.c
@@ -56,6 +56,7 @@
 	}
 
 	if (!tsk_used_math(tsk)) {
+		local_irq_enable();
 		/*
 		 * does a slab alloc which can sleep
 		 */
@@ -66,6 +67,7 @@
 			do_group_exit(SIGKILL);
 			return;
 		}
+		local_irq_disable();
 	}
 
 	grab_fpu(regs);