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

--- 2.6.14/arch/x86_64/kernel/entry.S	2005-10-28 02:02:08.000000000 +0200
+++ 2.6.14-x86_64-iret/arch/x86_64/kernel/entry.S	2005-11-07 14:56:02.000000000 +0100
@@ -751,7 +751,7 @@ error_exit:		
 	jnz  retint_careful
 	swapgs 
 	RESTORE_ARGS 0,8,0						
-	iretq
+	jmp iret_label
 	CFI_ENDPROC
 
 error_kernelspace: