[PATCH] Allow CONFIG_OF_FLAT_TREE to boot a non-arch/powerpc kernel

This patch allows an arch/ppc kernel to be booted by just passing 1 or 2
arguments to bootm.  It removes the getenv("disable_of") test that used
to be used for this purpose.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Jon Loeliger <jdl@freescale.com>