brcmfmac: Avoid usage of GFP_ATOMIC.

brcmfmac: Avoid usage of GFP_ATOMIC.

Msgbuf is using GFP_ATOMIC where GFP_KERNEL is also sufficient. On
some platforms the coherent DMA memory is very limited when using
GFP_ATOMIC. This patch changes usage of GFP_ATOMIC to GFP_KERNEL and
uses worker to make this possible for creation of flowring.

Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>