brcm80211: fmac: move chip recognition function to sdio_chip.c

Currently backplane handle code is scatterd around dhd_sdio.c which
is not good for maintenance and adding new backplane interconnect
type support. This patch and the follow up patches are going to
abstract all chip backplane control code specific for sdio bus
into this new sdio_chip.c

Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@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>