powerpc/mpc5200: fix bestcomm Kconfig dependencies

Without this patch it is possible to select drivers which require
bestcomm support without bestcomm support being selected.  This
patch reworks the bestcomm dependencies to ensure the correct
bestcomm tasks are always enabled.

Reported-by: Hans Lehmann <hans.lehmann@ritter-elektronik.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/sound/soc/fsl/Kconfig b/sound/soc/fsl/Kconfig
index bba9546..8d73edc 100644
--- a/sound/soc/fsl/Kconfig
+++ b/sound/soc/fsl/Kconfig
@@ -20,7 +20,8 @@
 
 config SND_SOC_MPC5200_I2S
 	tristate "Freescale MPC5200 PSC in I2S mode driver"
+	depends on SND_SOC && PPC_MPC52xx && PPC_BESTCOMM
 	select SND_SOC_OF_SIMPLE
-	depends on SND_SOC && PPC_MPC52xx
+	select PPC_BESTCOMM_GEN_BD
 	help
 	  Say Y here to support the MPC5200 PSCs in I2S mode.