arm64: mm: Remove superfluous "the" in comment

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>