ARM: imx7d: correct chip version information

The commond 'cat /sys/devices/soc0/revision' can
show correct soc version information.

"unknow revision" message in imx_print_silicon_rev()
will never work for digprog.
Signed-off-by: Frank Li <Frank.Li@freescale.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/mach-imx/anatop.c

@@ -151,7 +151,14 @@ void __init imx_init_revision_from_anatop(void)
 		revision = IMX_CHIP_REVISION_1_5;
 		break;
 	default:
-		revision = IMX_CHIP_REVISION_UNKNOWN;
+		/*
+		 * Fail back to return raw register value instead of 0xff.
+		 * It will be easy to know version information in SOC if it
+		 * can't be recognized by known version. And some chip's (i.MX7D)
+		 * digprog value match linux version format, so it needn't map
+		 * again and we can use register value directly.
+		 */
+		revision = digprog & 0xff;
 	}
 
 	mxc_set_cpu_type(digprog >> 16 & 0xff);