[ARM] 5416/1: Use unused address in v6_early_abort

The target of the strex instruction to clear the exlusive monitor
is currently the top of the stack.  If the store succeeeds this
corrupts r0 in pt_regs.  Use the next stack location instead of
the current one to prevent any chance of corrupting an in-use
address.
Signed-off-by: NSeth Forshee <seth.forshee@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/abort-ev6.S

@@ -23,7 +23,8 @@ ENTRY(v6_early_abort)
 #ifdef CONFIG_CPU_32v6K
 	clrex
 #else
-	strex	r0, r1, [sp]			@ Clear the exclusive monitor
+	sub	r1, sp, #4			@ Get unused stack location
+	strex	r0, r1, [r1]			@ Clear the exclusive monitor
 #endif
 	mrc	p15, 0, r1, c5, c0, 0		@ get FSR
 	mrc	p15, 0, r0, c6, c0, 0		@ get FAR