refinfra: add rdv3r1-bmc manifests for bmc support

Add pinned and non-pinned rdv3r1-bmc manifests variation which
introduces support for Baseboard Management Controllers communication
with RD-V3-R1 Neoverse Reference Design Platform.

Documentation at https://neoverse-reference-design.docs.arm.com

 provides
instructions to obtain and build the OpenBMC project, thus it is not
included in these manifests.

Signed-off-by: Nuno Lopes <nuno.lopes@arm.com>