IB/qib: Use GFP_ATOMIC when locks are held

alloc_dummy_hdrq() is called with locks held and thus should not use
GFP_KERNEL.

The semantic patch that makes this report is available in
scripts/coccinelle/locks/call_kern.cocci.

Signed-off-by: Julia Lawall <julia.lawall@lip6.fr>
Acked-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>