cpu: imx8: show RevC instead of Rev? at boot log

Add REVC informaiton.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/include/asm/arch-imx/cpu.h b/arch/arm/include/asm/arch-imx/cpu.h
index b525654..e9c0078 100644
--- a/arch/arm/include/asm/arch-imx/cpu.h
+++ b/arch/arm/include/asm/arch-imx/cpu.h
@@ -64,6 +64,7 @@
 
 #define CHIP_REV_A		0x0
 #define CHIP_REV_B		0x1
+#define CHIP_REV_C		0x2
 
 #define BOARD_REV_1_0           0x0
 #define BOARD_REV_2_0           0x1