brcmfmac: replace dongle command list with .preinit() callback

brcmfmac: replace dongle command list with .preinit() callback

The bus-specific interface allowed a list of dongle commands to be
provided to the common driver part. However, upcoming functionality
requires a more dynamic behaviour. Hence the list is replaced
by a new callback function so the bus-specific driver part can
implement this behaviour.

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>