MLK-19433-1 imx: Add macro for chip rev 2.1

Add common CHIP_REV_2_1 for chip revision 2.1
Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit f7fc83ffb0f204d9f6ec6c77c08d23869d9ecde4)

Change-Id: I20d5809902431fa7323083d3829b45058de27738
diff --git a/arch/arm/include/asm/arch-imx/cpu.h b/arch/arm/include/asm/arch-imx/cpu.h
index 57ec2a9..1e7d769 100644
--- a/arch/arm/include/asm/arch-imx/cpu.h
+++ b/arch/arm/include/asm/arch-imx/cpu.h
@@ -43,6 +43,7 @@
 #define CHIP_REV_1_2            0x12
 #define CHIP_REV_1_5            0x15
 #define CHIP_REV_2_0            0x20
+#define CHIP_REV_2_1            0x21
 #define CHIP_REV_2_5            0x25
 #define CHIP_REV_3_0            0x30