ARM: imx5: clean function declarations in mx51.h

The mx51_display_revision() is a dead declaration.  Remove it.  Also,
move mx51_revision() into common.h.
Signed-off-by: NShawn Guo <shawn.guo@freescale.com>

arch/arm/mach-imx/common.h

@@ -64,6 +64,7 @@ void mxc_set_cpu_type(unsigned int type);
 void mxc_restart(enum reboot_mode, const char *);
 void mxc_arch_reset_init(void __iomem *);
 void mxc_arch_reset_init_dt(void);
+int mx51_revision(void);
 int mx53_revision(void);
 void imx_set_aips(void __iomem *);
 int mxc_device_init(void);

arch/arm/mach-imx/mx51.h

@@ -305,9 +305,4 @@
 #define MX51_INT_EMI_NFC		(NR_IRQS_LEGACY + 101)
 #define MX51_INT_GPU_IDLE		(NR_IRQS_LEGACY + 102)
 
-#if !defined(__ASSEMBLY__) && !defined(__MXC_BOOT_UNCOMPRESS)
-extern int mx51_revision(void);
-extern void mx51_display_revision(void);
-#endif
-
 #endif	/* ifndef __MACH_MX51_H__ */