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>

arch/arm/mach-imx/common.h

@@ -77,6 +77,8 @@ extern int imx6q_revision(void);
 extern int mx53_display_revision(void);
 extern void imx_set_aips(void __iomem *);
 extern int mxc_device_init(void);
+void imx_set_soc_revision(unsigned int rev);
+unsigned int imx_get_soc_revision(void);
 
 enum mxc_cpu_pwr_mode {
 	WAIT_CLOCKED,		/* wfi only */

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)