ASoC: ux500: Fix dependencies

Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/ux500/Kconfig

@@ -4,6 +4,7 @@
 menuconfig SND_SOC_UX500
 	tristate "SoC Audio support for Ux500 platform"
 	depends on SND_SOC
+	depends on MFD_DB8500_PRCMU
 	help
 		Say Y if you want to enable ASoC-support for
 		any of the Ux500 platforms (e.g. U8500).