ASoC: dwc: Bodge around continuing absence of clock API stubs

The patches for stubbing out the generic clock API still haven't been
applied so we need to either add ifdefs here or add a dependency until
someone decides to actually apply them.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/dwc/Kconfig

 config SND_DESIGNWARE_I2S
 	tristate "Synopsys I2S Device Driver"
+	depends on CLKDEV_LOOKUP
 	help
 	 Say Y or M if you want to add support for I2S driver for
 	 Synopsys desigwnware I2S device. The device supports upto