ARM: imx: add soc revision helper functions

Similar to what we do for cpu type, the patch adds helper functions
imx_set_soc_revision() and imx_get_soc_revision() to maintain
imx_soc_revision in cpu.c.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-imx/cpu.c b/arch/arm/mach-imx/cpu.c
index e70e3ac..51f6c51 100644
--- a/arch/arm/mach-imx/cpu.c
+++ b/arch/arm/mach-imx/cpu.c
@@ -8,11 +8,23 @@
 unsigned int __mxc_cpu_type;
 EXPORT_SYMBOL(__mxc_cpu_type);
 
+static unsigned int imx_soc_revision;
+
 void mxc_set_cpu_type(unsigned int type)
 {
 	__mxc_cpu_type = type;
 }
 
+void imx_set_soc_revision(unsigned int rev)
+{
+	imx_soc_revision = rev;
+}
+
+unsigned int imx_get_soc_revision(void)
+{
+	return imx_soc_revision;
+}
+
 void imx_print_silicon_rev(const char *cpu, int srev)
 {
 	if (srev == IMX_CHIP_REVISION_UNKNOWN)