s390/alternatives: avoid using jgnop mnemonic

jgnop mnemonic is only available since binutils 2.36,
kernel minimal required version is 2.23. Stick to brcl
to avoid build errors.
Reported-by: Nathan Chancellor <nathan@kernel.org>
Fixes: 4afeb670 ("s390/alternatives: use instructions instead of byte patterns")
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/alternative-asm.h

@@ -38,7 +38,7 @@
  */
 .macro alt_pad_fill bytes
 	.rept	( \bytes ) / 6
-	jgnop	.
+	brcl	0,0
 	.endr
 	.rept	( \bytes ) % 6 / 4
 	nop

arch/s390/include/asm/alternative.h

@@ -75,7 +75,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 	"\tnopr\n"							\
 	".else\n"							\
 	"\t.rept " oldinstr_pad_len(num) " / 6\n"			\
-	"\t.jgnop .\n"							\
+	"\t.brcl 0,0\n"							\
 	"\t.endr\n"							\
 	"\t.rept " oldinstr_pad_len(num) " %% 6 / 4\n"			\
 	"\tnop\n"							\