brcmfmac: decouple set_sbaddr_window from register write interface

brcmf_sdcard_set_sbaddr_window configures 3 registers on SDIO
function misc bank to change current silicon backplane programming
window. This patch makes it call brcmf_sdioh_request_byte directly
in order to prepare for the write register interface unification.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>