ARM: 8238/1: mm: Refine set_memory_* functions

set_memory_* functions have same implementation
except memory attribute.

This patch makes to use common function for these, and pull out
the functions into arch/arm/mm/pageattr.c like arm64 did.
It will reduce code size and enhance the readability.

Signed-off-by: Jungseung Lee <js07.lee@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>