arm/boot: Free dtb blob memory after use

arm/boot: Free dtb blob memory after use

The dtb blob returned by load_device_tree() is in memory allocated
with g_malloc(). Free it accordingly once we have copied its
contents into the guest memory. To make this easy, we need also to
clean up the error handling in load_dtb() so that we consistently
handle errors in the same way (by printing a message and then
returning -1, rather than either plowing on or exiting immediately).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Message-id: 1371209256-11408-1-git-send-email-peter.maydell@linaro.org