wlcore: use GFP_KERNEL together with GFP_DMA

GFP_DMA should not be used by itself, it still needs GFP_KERNEL or
such.  Fix two occurrences of allocations with GFP_DMA only.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>