feat(rdfremont): introduce initial rdfremont platform support

RD-Fremont Fixed Virtual Platform is an Arm Neoverse Reference Design
platform with ARMv9 RME enabled CPUs and 2 DRAM banks. Add initial
platform support by adding the required platform configuration file
that includes RMM size and granule information.

Signed-off-by: Harry Moulton <harry.moulton@arm.com>
Change-Id: I2c7330fde0ac51ffd5d3100017268ba9246b4b4d