KVM: s390: use pid of cpu thread for sampling tagging

Right now we use the address of the sie control block as tag for
the sampling data. This is hard to get for users. Let's just use
the PID of the cpu thread to mark the hardware samples.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

@@ -199,7 +199,7 @@ ENTRY(sie64a)
 	jo	.Lsie_skip			# exit if fp/vx regs changed
 	tm	__LC_MACHINE_FLAGS+6,0x20	# MACHINE_FLAG_LPP
 	jz	.Lsie_enter
-	.insn	s,0xb2800000,__SF_EMPTY(%r15)	# set guest id
+	.insn	s,0xb2800000,__LC_CURRENT_PID	# set guest id to pid
 .Lsie_enter:
 	sie	0(%r14)
 	tm	__LC_MACHINE_FLAGS+6,0x20	# MACHINE_FLAG_LPP