remoteproc: Introduce K3 remoteproc driver for R5F subsystem

SoCs with K3 architecture have an integrated Arm Cortex-R5F subsystem
that is comprised of dual-core Arm Cortex-R5F processor cores. This R5
subsytem can be configured at boot time to be either run in a LockStep
mode or in an Asymmetric Multi Processing (AMP) fashion in Split-mode.
This subsystem has each Tightly-Coupled Memory (TCM) internal memories
for each core split between two banks - TCMA and TCMB.

Add a remoteproc driver to support this subsystem to be able to load
and boot the R5 cores primarily in LockStep mode or split mode.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>