brcmfmac: Dynamically register a protocol layer.

BCDC is the default protocol layer and being called directly. This
patch installs the functions for this layer dynamically. This allows
new protocols to be added and selected dynamically depending on the
hw capabilties. As currently only BCDC is supported this is always
the installed protocol.

Reviewed-by: Arend Van Spriel <arend@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>