vTPM: fix memory allocation flag for rtce buffer at kernel boot

commit 60ecd86c4d985750efa0ea3d8610972b09951715 upstream.

At ibm vtpm initialzation, tpm_ibmvtpm_probe() registers its interrupt
handler, ibmvtpm_interrupt, which calls ibmvtpm_crq_process to allocate
memory for rtce buffer.  The current code uses 'GFP_KERNEL' as the
type of kernel memory allocation, which resulted a warning at
kernel/lockdep.c.  This patch uses 'GFP_ATOMIC' instead so that the
allocation is high-priority and does not sleep.

Signed-off-by: Hon Ching(Vicky) Lo <honclo@linux.vnet.ibm.com>
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>