brcmfmac: Combine protocol push hdr and bus txdata.

For the transmission of data a protocol push hdr is performed
followed by a bus txdata call. For the new protocol msgbuf this
is not workable. Since they are already "loosely" coupled for
bcdc protocol they are combined. This means that txdata will
go "through" the protocol layer and a seperate protocol push
hdr will not be needed anymore.

Reviewed-by: Arend Van Spriel <arend@broadcom.com>
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>