Remove unprotected iret

From: Jan Beulich <jbeulich@novell.com>

Make sure no iret can fault without attached recovery code.
Cannot happen in the normal case, but might be useful
with kernel debuggers

Signed-off-by: Andi Kleen <ak@suse.de>

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -754,7 +754,7 @@ error_exit:		
 	jnz  retint_careful
 	swapgs 
 	RESTORE_ARGS 0,8,0						
-	iretq
+	jmp iret_label
 	CFI_ENDPROC
 
 error_kernelspace: