brcmfmac: remove .init() callback for internal bus interface

brcmfmac: remove .init() callback for internal bus interface

The .init() callback was the first function called by the common
bus function brcmf_bus_start(). Given that it is not really
necessary and the bus layer can call it before calling the
brcmf_bus_start() function.

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