env: ti: j721e-evm: Add support to boot rprocs including R5Fs and DSPs

env: ti: j721e-evm: Add support to boot rprocs including R5Fs and DSPs

Add support to boot some remoteprocs at U-boot prompt on the J721E EVM
boards by using the 'boot_rprocs' and other env variables defined in the
common environment file k3_rproc.h, and updating the 'DEFAULT_RPROCS'
macro.

The list of R5F cores to be started before loading and booting the Linux
kernel are as follows, and in this order:
   Main R5FSS0 (Split) Core1 : 3 /lib/firmware/j7-main-r5f0_1-fw
   Main R5FSS1 (LockStep)    : 4 /lib/firmware/j7-main-r5f1_0-fw

The MCU R5FSS0 and Main R5FSS1 are currently in LockStep mode, so the
equivalent Core1 rprocs (rproc #1 and #5) are not included. The Main
R5FSS0 Core0 (rproc #2) is already started by R5 SPL, so is not included
in the list either.

The DSP cores are started in the following order before loading and
booting the Linux kernel:
   C66_0: 6 /lib/firmware/j7-c66_0-fw
   C66_1: 7 /lib/firmware/j7-c66_1-fw
   C71_0: 8 /lib/firmware/j7-c71_0-fw

The order of the rprocs to boot can be changed at runtime if desired by
overwriting the 'rproc_fw_binaries' environment variable at U-boot prompt.

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