arm64: kexec: Make crash_is_nosave() aware of kexec using crashk_res

arm64's hibernate code save/restores the kdump kernel in the crash
kernel region. To avoid saving the whole region, crash_is_nosave()
identifies parts of this region that are not part of the kdump image.

Once kexec starts using this region too, the hibernate code needs
to check both images for an overlap with the provided address.

Signed-off-by: James Morse <james.morse@arm.com>