s390/pci: fix sleeping in atomic during hotplug

When triggered by pci hotplug (PEC 0x306) clp_get_state is called
with spinlocks held resulting in the following warning:

zpci: n/a: Event 0x306 reconfigured PCI function 0x0
BUG: sleeping function called from invalid context at mm/page_alloc.c:4324
in_atomic(): 1, irqs_disabled(): 0, pid: 98, name: kmcheck
2 locks held by kmcheck/98:

Change the allocation to use GFP_ATOMIC.

Cc: stable@vger.kernel.org # 4.13+
Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci_clp.c

@@ -436,7 +436,7 @@ int clp_get_state(u32 fid, enum zpci_state *state)
 	struct clp_state_data sd = {fid, ZPCI_FN_STATE_RESERVED};
 	int rc;
 
-	rrb = clp_alloc_block(GFP_KERNEL);
+	rrb = clp_alloc_block(GFP_ATOMIC);
 	if (!rrb)
 		return -ENOMEM;