ARM: 8706/1: NOMMU: Move out MPU setup in separate module

Having MPU handling code in dedicated module makes it easier to
enhance/maintain it.

Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>