[PATCH] staging: wfx: fix an undefined reference error when CONFIG_MMC=m

[zhong jiang]

I hit the following error when compile the kernel.

drivers/staging/wfx/main.o: In function `wfx_core_init':
/home/z00352263/linux-next/linux-next/drivers/staging/wfx/main.c:488: undefined reference to `sdio_register_driver'
drivers/staging/wfx/main.o: In function `wfx_core_exit':
/home/z00352263/linux-next/linux-next/drivers/staging/wfx/main.c:496: undefined reference to `sdio_unregister_driver'
drivers/staging/wfx/main.o:(.debug_addr+0x1a8): undefined reference to `sdio_register_driver'
drivers/staging/wfx/main.o:(.debug_addr+0x6f0): undefined reference to `sdio_unregister_driver'

Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
---
 drivers/staging/wfx/Kconfig  | 3 ++-
 drivers/staging/wfx/Makefile | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/wfx/Kconfig b/drivers/staging/wfx/Kconfig
index 9b8a1c7..4d045513 100644
--- a/drivers/staging/wfx/Kconfig
+++ b/drivers/staging/wfx/Kconfig
@@ -1,7 +1,8 @@
 config WFX
 	tristate "Silicon Labs wireless chips WF200 and further"
 	depends on MAC80211
-	depends on (SPI || MMC)
+	depends on SPI
+	select MMC
 	help
 	  This is a driver for Silicons Labs WFxxx series (WF200 and further)
 	  chipsets. This chip can be found on SPI or SDIO buses.
diff --git a/drivers/staging/wfx/Makefile b/drivers/staging/wfx/Makefile
index 0d9c1ed..fc30b49 100644
--- a/drivers/staging/wfx/Makefile
+++ b/drivers/staging/wfx/Makefile
@@ -17,8 +17,9 @@ wfx-y := \
 	key.o \
 	main.o \
 	sta.o \
-	debug.o
+	debug.o \
+	bus_sdio.o
+
 wfx-$(CONFIG_SPI) += bus_spi.o
-wfx-$(subst m,y,$(CONFIG_MMC)) += bus_sdio.o
 
 obj-$(CONFIG_WFX) += wfx.o
-- 
1.7.12.4