Fix initrd length corruption in bootm command.

When using FDT Images, the length of an inital ramdisk was
overwritten (bug introduced by commit 87a449c8, 22 Aug 2006).

Patches by Timur Tabi & Johns Daniel.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index 32c29e5..a6499e8 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -779,9 +779,8 @@
 
 			checksum = ntohl(hdr->ih_dcrc);
 			addr = (ulong)((uchar *)(hdr) + sizeof(image_header_t));
-			len = ntohl(hdr->ih_size);
 
-			if(checksum != crc32(0, (uchar *)addr, len)) {
+			if(checksum != crc32(0, (uchar *)addr, ntohl(hdr->ih_size))) {
 				printf("ERROR: Flat Device Tree checksum is invalid\n");
 				return;
 			}