s390/suspend: fix prefix register reset in swsusp_arch_resume

The reset of the prefix to zero in swsusp_arch_resume uses a 4 byte stack
slot. With CONFIG_VMAP_STACK=y this is now in the vmalloc area, this works
only with DAT enabled. Move the DAT disable in swsusp_arch_resume after
the prefix reset.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/swsusp.S

@@ -124,13 +124,13 @@ ENTRY(swsusp_arch_resume)
 	lghi	%r2,1
 	brasl	%r14,arch_set_page_states
 
-	/* Deactivate DAT */
-	stnsm	__SF_EMPTY(%r15),0xfb
-
 	/* Set prefix page to zero */
 	xc	__SF_EMPTY(4,%r15),__SF_EMPTY(%r15)
 	spx	__SF_EMPTY(%r15)
 
+	/* Deactivate DAT */
+	stnsm	__SF_EMPTY(%r15),0xfb
+
 	/* Restore saved image */
 	larl	%r1,restore_pblist
 	lg	%r1,0(%r1)