ntb: ntb_transport: Replace GFP_ATOMIC with GFP_KERNEL in ntb_transport_setup_qp_mw

ntb_transport_setup_qp_mw() is never called in atomic context.

ntb_transport_setup_qp_mw() is only called by ntb_transport_link_work(),
which is set as a parameter of INIT_DELAYED_WORK()
in ntb_transport_probe().

Despite never getting called from atomic context,
ntb_transport_setup_qp_mw() calls kzalloc_node() with GFP_ATOMIC,
which does not sleep for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
which can sleep and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>