brcm80211: fmac: add Kconfig option for SDIO bus support

This patch adds a Kconfig option for SDIO bus support and abstracts
a build subset correspondingly. It's the final patch of fullmac bus
interface refactoring.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/brcm80211/Kconfig b/drivers/net/wireless/brcm80211/Kconfig
index 8f54c2e..cd6375d 100644
--- a/drivers/net/wireless/brcm80211/Kconfig
+++ b/drivers/net/wireless/brcm80211/Kconfig
@@ -17,16 +17,26 @@
 
 config BRCMFMAC
 	tristate "Broadcom IEEE802.11n embedded FullMAC WLAN driver"
-	depends on MMC
 	depends on CFG80211
 	select BRCMUTIL
-	select FW_LOADER
 	---help---
 	  This module adds support for embedded wireless adapters based on
-	  Broadcom IEEE802.11n FullMAC chipsets.  This driver uses the kernel's
-	  wireless extensions subsystem.  If you choose to build a module,
+	  Broadcom IEEE802.11n FullMAC chipsets. It has to work with at least
+	  one of the bus interface support. If you choose to build a module,
 	  it'll be called brcmfmac.ko.
 
+config BRCMFMAC_SDIO
+	bool "SDIO bus interface support for FullMAC"
+	depends on MMC
+	depends on BRCMFMAC
+	select FW_LOADER
+	default y
+	---help---
+	  This option enables the SDIO bus interface support for Broadcom
+	  FullMAC WLAN driver.
+	  Say Y if you want to use brcmfmac for a compatible SDIO interface
+	  wireless card.
+
 config BRCMDBG
 	bool "Broadcom driver debug functions"
 	depends on BRCMSMAC || BRCMFMAC