corstone-310: Enable MPS3-IO on non-secure side

Most of the applications would be using input-output
peripheral to drive LEDs, sensors, etc..

This commit is added to enable the MPS3 input-output
peripheral on corstone-310 platform to be used on the
non-secure side from which the user application would
be executed.

Signed-off-by: Ahmed Ismail <Ahmed.Ismail@arm.com>