[S390] fix single stepped svcs with TRACE_IRQFLAGS=y

If irq flags tracing is enabled the TRACE_IRQS_ON macros expands to
a function call which clobbers registers %r0-%r5. The macro is used
in the code path for single stepped system calls. The argument
registers %r2-%r6 need to be restored from the stack before the system
call function is called.

Cc: stable@kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

@@ -571,6 +571,7 @@ pgm_svcper:
 	mvc	__THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID
 	oi	__TI_flags+3(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
 	TRACE_IRQS_ON
+	lm	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
 	b	BASED(sysc_do_svc)
 

arch/s390/kernel/entry64.S

@@ -549,6 +549,7 @@ pgm_svcper:
 	mvc	__THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID
 	oi	__TI_flags+7(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
 	TRACE_IRQS_ON
+	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
 	j	sysc_do_svc