ARM: imx: don't build ssi-fiq if not required

The symbols provided by ssi-fiq are used in sound/soc/fsl/imx-pcm-fiq.c
only. Build ssi-fiq.o/ssi-fiq-ksym.o only if SND_SOC_IMX_PCM_FIQ is
enabled.
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/mach-imx/Makefile

@@ -31,7 +31,7 @@ obj-$(CONFIG_SOC_IMX6SX) += cpuidle-imx6sx.o
 obj-$(CONFIG_SOC_IMX6UL) += cpuidle-imx6sx.o
 endif
 
-ifdef CONFIG_SND_IMX_SOC
+ifdef CONFIG_SND_SOC_IMX_PCM_FIQ
 obj-y += ssi-fiq.o
 obj-y += ssi-fiq-ksym.o
 endif