ARM: 7304/1: ioremap: fix boundary check when reusing static mapping

Since commit 576d2f25 "ARM: add
generic ioremap optimization by reusing static mappings" ioremap()
is trying to reuse existing static mapping when possible.

The condition checking boundaries of the requested and existing
mappings didn't take in-page offset into consideration though,
which lead to obscure and hard to debug problems when requested
mapping crossed end of the static one.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>