s390/sclp: sign extend return value of _sclp_print_early()

_sclp_print_early() has a return value, but misses to sign extend it
if called from 64 bit code.
This is not really a bug, since currently no caller cares what the
return value is.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/sclp.S

@@ -294,7 +294,8 @@ ENTRY(_sclp_print_early)
 #ifdef CONFIG_64BIT
 	tm	LC_AR_MODE_ID,1
 	jno	.Lesa3
-	lmh	%r6,%r15,96(%r15)		# store upper register halves
+	lgfr	%r2,%r2				# sign extend return value
+	lmh	%r6,%r15,96(%r15)		# restore upper register halves
 	ahi	%r15,80
 .Lesa3:
 #endif