s390/pci: fix sleeping in atomic during hotplug

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>