[U-Boot] Regression due to: arm: Add Prep subcommand support to bootm

[Stephen Warren]

I just tried the latest u-boot/master, at commit:

3f0675d Merge branch 'marek.vasut at gmail.com' of
git://git.denx.de/u-boot-staging

This fails to boot a Linux kernel on my ARM Tegra board; the boot log is:

====================
## Booting kernel from Legacy Image at 00408000 ...
Image Name: Linux-3.4.0-rc1-next-20120405-00
Image Type: ARM Linux Kernel Image (no loading done) (uncompressed)
Data Size: 2756424 Bytes = 2.6 MiB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
## Flattened Device Tree blob at 01000000
Booting using the fdt blob at 0x01000000
XIP Kernel Image (no loading done) ... OK
OK
Loading Device Tree to 010fa000, end 010ff726 ... OK

Starting kernel ...

Uncompressing Linux... done, booting the kernel.
Warning: Neither atags nor dtb found
====================

If I revert commit 0a672d4 "arm: Add Prep subcommand support to bootm",
then everything works fine again.