plat(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 build configuration
files. This change introduces a new config file that includes the DRAM
bank information, RMM size and granule information, and UART address.

The platform shares the initial plat_setup code with FVP.

Signed-off-by: Sathyam Panda <sathyam.panda@arm.com>
Signed-off-by: Harry Moulton <harry.moulton@arm.com>
Change-Id: Id3df2c7f461b5ed8e320e0c0e0a92917c1610234