Fix memory region setup after NPU reset

Currently the NPU's memory regions are only setup during the device
initialization and are lost when the NPU is reset. To resolve this, the
memory regions are now setup after each reset of the NPU.

Change-Id: I8ffa41c544f90b3756c02a9d708f0fff112f5e51
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>