b43: drop SSB dependency

This adds choice submenu "Supported bus types" as two simple bool
configs would allow user to compile b43 without any bus support
(prety useless).
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/Kconfig

 config B43
 	tristate "Broadcom 43xx wireless support (mac80211 stack)"
-	depends on SSB_POSSIBLE && MAC80211 && HAS_DMA
-	select SSB
+	depends on (BCMA_POSSIBLE || SSB_POSSIBLE) && MAC80211 && HAS_DMA
+	select BCMA if B43_BCMA
+	select SSB if B43_SSB
 	select FW_LOADER
 	---help---
 	  b43 is a driver for the Broadcom 43xx series wireless devices.
@@ -27,14 +28,33 @@ config B43
 	  If unsure, say M.
 
 config B43_BCMA
-	bool "Support for BCMA bus"
-	depends on B43 && (BCMA = y || BCMA = B43)
-	default y
+	bool
 
 config B43_SSB
 	bool
-	depends on B43 && (SSB = y || SSB = B43)
-	default y
+
+choice
+	prompt "Supported bus types"
+	depends on B43
+	default B43_BCMA_AND_SSB
+
+config B43_BUSES_BCMA_AND_SSB
+	bool "BCMA and SSB"
+	depends on BCMA_POSSIBLE && SSB_POSSIBLE
+	select B43_BCMA
+	select B43_SSB
+
+config B43_BUSES_BCMA
+	bool "BCMA only"
+	depends on BCMA_POSSIBLE
+	select B43_BCMA
+
+config B43_BUSES_SSB
+	bool "SSB only"
+	depends on SSB_POSSIBLE
+	select B43_SSB
+
+endchoice
 
 # Auto-select SSB PCI-HOST support, if possible
 config B43_PCI_AUTOSELECT
@@ -98,7 +118,7 @@ config B43_BCMA_PIO
 
 config B43_PIO
 	bool
-	depends on B43
+	depends on B43 && B43_SSB
 	select SSB_BLOCKIO
 	default y