ixgbe: Replace GFP_ATOMIC with GFP_KERNEL

ixgbe_fcoe_ddp_setup(), ixgbe_setup_fcoe_ddp_resources() and
ixgbe_sw_init() are never called in atomic context.
They call kmalloc(), dma_pool_alloc() and kzalloc() with GFP_ATOMIC,
which is not necessary.
GFP_ATOMIC can be replaced with GFP_KERNEL.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Acked-by: Sebastian Basierski <sebastianx.basierski@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>