brcmfmac: dont use ZERO flag for usb IN

URB_ZERO_PACKET should only be set or bulk OUT and this condition
is checked with a WARN_ON in usb_submit_urb(). This patch fixes
brcmfmac to get rid of this warning filling the logs.

Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@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>