Commit 19accfd3 (ARM: move vector stubs) moved the vector stubs in an
additional page above the base vector one. This change wasn't taken into
account by the nommu memreserve.
This patch ensures that the kernel won't overwrite any vector stub on
nommu.

[changed the MPU side too]
Signed-off-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: NVladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>