ARM: mx31: use generic function for displaying silicon revision

Update to use generic function for displaying silicon revision

Tested on mx31pdk board as print the following information:
CPU identified as i.MX31, silicon rev 2.0

Signed-off-by: Jason Liu <jason.hui@linaro.org>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/plat-mxc/include/mach/mx3x.h b/arch/arm/plat-mxc/include/mach/mx3x.h
index 388a407..e1850f4 100644
--- a/arch/arm/plat-mxc/include/mach/mx3x.h
+++ b/arch/arm/plat-mxc/include/mach/mx3x.h
@@ -187,15 +187,6 @@
 /* Mandatory defines used globally */
 
 #if !defined(__ASSEMBLY__) && !defined(__MXC_BOOT_UNCOMPRESS)
-
-extern unsigned int mx31_cpu_rev;
-extern void mx31_read_cpu_rev(void);
-
-static inline int mx31_revision(void)
-{
-	return mx31_cpu_rev;
-}
-
 extern unsigned int mx35_cpu_rev;
 extern void mx35_read_cpu_rev(void);
 
@@ -203,6 +194,8 @@
 {
 	return mx35_cpu_rev;
 }
+
+extern int mx31_revision(void);
 #endif
 
 #endif /* ifndef __MACH_MX3x_H__ */