brcm80211: fmac: chip attach code flow clean up

Merged brcmf_sdbrcm_chip_attach into brcmf_sdio_chip_attach
for better readability.

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