[S390] Fix FCP dump feature detection.

FCP dump feature detection works only if the sclp command in head.S
was succesful. Since the sclp command is skipped if diag260 works,
we don't have any dump feature detection anymore.
Bug was introduced with d57de5a367.

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

arch/s390/kernel/head64.S

@@ -81,7 +81,6 @@ startup_continue:
 	aghi	%r1,1			# size is one more than end
 	larl	%r2,memory_chunk
 	stg	%r1,8(%r2)		# store size of chunk
-	j	.Ldonemem
 
 .Lslowmemdetect:
 	l	%r2,.Lrcp-.LPG1(%r13)	# Read SCP forced command word
@@ -156,6 +155,11 @@ startup_continue:
 #
 # find memory chunks.
 #
+	larl	%r9,memory_chunk	# skip tprot loop if diag260
+	lg	%r9,8(%r9)		# memory detection was successful
+	ltgr	%r9,%r9
+	jne	.Ldonemem
+
 	lgr	%r9,%r3			# end of mem
 	larl	%r1,.Lchkmem		# set program check address
 	stg	%r1,__LC_PGM_NEW_PSW+8