arm64: dts: ti: k3-j721e-main: Add MAIN domain R5F cluster nodes

arm64: dts: ti: k3-j721e-main: Add MAIN domain R5F cluster nodes

The J721E SoCs have 3 dual-core Arm Cortex-R5F processor (R5FSS)
subsystems/clusters. One R5F cluster (MCU_R5FSS0) is present within
the MCU domain, and the remaining two clusters are present in the
MAIN domain (MAIN_R5FSS0 & MAIN_R5FSS1). Each of these 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. These
subsystems have 64 KB each Tightly-Coupled Memory (TCM) internal
memories for each core split between two banks - ATCM and BTCM
(further interleaved into two banks). There are some IP integration
differences from standard Arm R5 clusters such as the absence of
an ACP port, presence of an additional TI-specific Region Address
Translater (RAT) module for translating 32-bit CPU addresses into
larger system bus addresses etc.

Add the DT nodes for these two MAIN domain R5F cluster/subsystems,
the two R5F cores are each added as child nodes to the corresponding
main cluster node. Both the clusters are configured to run in LockStep
mode by default, with the ATCMs enabled to allow the R5 cores to execute
code from DDR with boot-strapping code from ATCM. The inter-processor
communication between the main A72 cores and these processors is
achieved through shared memory and Mailboxes.

The following firmware names are used by default for these cores, and
can be overridden in a board dts file if needed:
    MAIN R5FSS0 Core0: j7-main-r5f0_0-fw (both in LockStep and Split modes)
    MAIN R5FSS0 Core1: j7-main-r5f0_1-fw (needed only in Split mode)
    MAIN R5FSS1 Core0: j7-main-r5f1_0-fw (both in LockStep and Split modes)
    MAIN R5FSS1 Core1: j7-main-r5f1_1-fw (needed only in Split mode)

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20201029033802.15366-7-s-anna@ti.com