s390/amode31: Use exrl instead of ex

exrl is present in all machines currently supported, therefore prefer
it over ex. This saves one instruction and doesn't need an additional
register to hold the address of the target instruction.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: svens-s390

arch/s390/kernel/text_amode31.S

@@ -18,8 +18,7 @@
  * affects a few functions that are not performance-relevant.
  */
 	.macro BR_EX_AMODE31_r14
-	larl	%r1,0f
-	ex	0,0(%r1)
+	exrl	0,0f
 	j	.
 0:	br	%r14
 	.endm