wifi: brcmfmac: add function to unbind device to bus layer api

wifi: brcmfmac: add function to unbind device to bus layer api

Introduce a new bus callback .remove() which will unbind the device
from the driver. This allows the common driver layer to stop handling
a device.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221129135446.151065-2-arend.vanspriel@broadcom.com