mwifiex: remove redundant GFP_DMA flag

skb forwarded to TCP/IP stack doesn't need to allocate in DMA ZONE.
This patch removes GFP_DMA flag in this case to save precious DMA
memory.

Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>