[S390] compile fix for latest binutils

The latest binutils won't accept the stfl instruction with march=g5
which is the correct behaviour. Unfortunately head.S is assembled
with -march=g5 even if the target cpu is z900 or later. To get
31-bit kernels compiled again the easiest fix is to use the .insn
notation for the stfl instruction in head.S.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/head.S

@@ -460,7 +460,7 @@ startup:
 #ifndef CONFIG_MARCH_G5
 	# check capabilities against MARCH_{G5,Z900,Z990,Z9_109,Z10}
 	xc	__LC_STFL_FAC_LIST(8),__LC_STFL_FAC_LIST
-	stfl	__LC_STFL_FAC_LIST	# store facility list
+	.insn	s,0xb2b10000,__LC_STFL_FAC_LIST	# store facility list
 	tm	__LC_STFL_FAC_LIST,0x01	# stfle available ?
 	jz	0f
 	la	%r0,0