brcmfmac: move allocation of control rx buffer to brcmf_sdio_bus_preinit()

Allocate the control rx buffer needed for firmware control interface
during brcmf_sdio_bus_preinit(). This relies on common layer setting
struct brcmf_bus::maxctl during brcmf_attach(). By moving the allocation
we can move brcmf_attach() in subsequent change.

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@codeaurora.org>