[ARM] head.S change broke platform device registration?

[Marko Katić]

I recently tried to boot v3.7-rc7 on my akita (Sharp Zaurus C-1000,
PXA270 machine).
Backlight never turned on but the kernel booted just fine.
After some investigation i determined that the gpio expander (max7310,
i2c chip) is not even
registered and thus not present in /sys/bus/i2c/devices.
Backlight gpio controls are hooked to this chip thus, no backlight.

I thought that too many things could have caused this so i went
straight to bisecting.
Bisection pointed me to this commit:

 commit 424e5994e63326a42012f003f1174f3c363c7b62
Author: Dave Martin <dave.martin at linaro.org>
Date:   Fri Feb 10 18:07:07 2012 -0800

    ARM: zImage/virt: hyp mode entry support for the zImage loader

    The zImage loader needs to turn on the MMU in order to take
    advantage of caching while decompressing the zImage.  Running this
    in hyp mode would require the LPAE pagetable format to be
    supported; to avoid this complexity, this patch switches out of hyp
    mode, and returns back to hyp mode just before booting the kernel.

    This implementation assumes that the Hyp mode view of memory and the
    PL1 view of memory are coherent, providing that the MMU and caches
    are off in both, as required by the boot protocol.  The zImage
    decompression code must drain the write buffer on completion anyway, and
    entry into Hyp mode should flush any prefetch buffer, avoiding hazards
    associated with local write buffers and the pipeline.

    Signed-off-by: Dave Martin <dave.martin at linaro.org>
    Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>

This commit was merged in v3.7-rc1. And indeed, if i
revert this single commit, my gpio expander reappears and
so does my backlight.
I made no other changes to the vanilla 3.7-rc7
except this revert.

This seems very strange to me because i, with my limited knowledge,
cannot see any correlation between this commit and the bug i am experiencing.

Does anyone know what exactly is happening here?