s390/lib: Use exrl instead of ex in string functions

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

Reviewed-by: Heiko Carstens <[e-mail]>
Signed-off-by: Sven Schnelle <[e-mail]>
Signed-off-by: Alexander Gordeev <[e-mail]>

arch/s390/lib/mem.S

···
 	la	%r3,256(%r3)
 	brctg	%r0,.Lmemmove_forward_loop
 .Lmemmove_forward_remainder:
-	larl	%r5,.Lmemmove_mvc
-	ex	%r4,0(%r5)
+	exrl	%r4,.Lmemmove_mvc
 .Lmemmove_exit:
 	BR_EX	%r14
 .Lmemmove_reverse:
···
 	la	%r1,256(%r1)
 	brctg	%r3,.Lmemset_clear_loop
 .Lmemset_clear_remainder:
-	larl	%r3,.Lmemset_xc
-	ex	%r4,0(%r3)
+	exrl	%r4,.Lmemset_xc
 .Lmemset_exit:
 	BR_EX	%r14
 .Lmemset_fill:
···
 	brctg	%r5,.Lmemset_fill_loop
 .Lmemset_fill_remainder:
 	stc	%r3,0(%r1)
-	larl	%r5,.Lmemset_mvc
-	ex	%r4,0(%r5)
+	exrl	%r4,.Lmemset_mvc
 	BR_EX	%r14
 .Lmemset_fill_exit:
 	stc	%r3,0(%r1)
···
 	lgr	%r1,%r2
 	jnz	.Lmemcpy_loop
 .Lmemcpy_remainder:
-	larl	%r5,.Lmemcpy_mvc
-	ex	%r4,0(%r5)
+	exrl	%r4,.Lmemcpy_mvc
 .Lmemcpy_exit:
 	BR_EX	%r14
 .Lmemcpy_loop:
···
 	brctg	%r5,.L__memset_loop\bits
 .L__memset_remainder\bits:
 	\insn	%r3,0(%r1)
-	larl	%r5,.L__memset_mvc\bits
-	ex	%r4,0(%r5)
+	exrl	%r4,.L__memset_mvc\bits
 	BR_EX	%r14
 .L__memset_store\bits:
 	\insn	%r3,0(%r2)