drivers/tzc-dmc620: add driver to setup DMC-620 TZC controller

ARM CoreLink DMC-620 Dynamic Memory Controller includes a TZC controller
to setup secure or non-secure regions of DRAM memory. The TZC controller
allows to setup upto eight such regions of memory in DRAM. This driver
provides helper functions to setup the TZC controller within DMC-620.

Change-Id: Iee7692417c2080052bdb7b1c2873a024bc5d1d10
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>