mxc: Define architecture identifier

Define ARCH_MXC for i.MX devices. This is useful to identify features or
behaviors common to all i.MX SoCs.

The i.MX28 is omitted because its architecture is a bit different (like imx/mxc
vs. mxs in Linux).

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Andy Fleming <afleming@gmail.com>
Cc: Kim Phillips <kim.phillips@freescale.com>
diff --git a/arch/arm/include/asm/arch-mx27/imx-regs.h b/arch/arm/include/asm/arch-mx27/imx-regs.h
index f78d5f2..2f6c823 100644
--- a/arch/arm/include/asm/arch-mx27/imx-regs.h
+++ b/arch/arm/include/asm/arch-mx27/imx-regs.h
@@ -196,6 +196,8 @@
 
 #endif
 
+#define ARCH_MXC
+
 #define IMX_IO_BASE		0x10000000
 
 #define IMX_AIPI1_BASE		(0x00000 + IMX_IO_BASE)