ARM: zImage: the page table memory must be considered before relocation

For correctness, the initial page table located right before the
decompressed kernel should be considered when determining if relocation
is required.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>