arm: mach-k3: j721e: Split out J7200 SoC support from J721e

arm: mach-k3: j721e: Split out J7200 SoC support from J721e

Currently in j721e_init.c we check which firewalls to remove using
the board configuration (e.g CONFIG_TARGET_J721E_R5_EVM). We do this
as J721e and J7200 have different IP and firewalls but use the same
SoC definition (SOC_K3_J721E) even though they are different SoCs.

The idea was they would be similar enough that they both could use
the same SoC config to help with common code sharing. Board checks
would then be used differentiate.

This has grown far too messy to maintain any more, especially now
that there is more than one board using J721e (EVM, SK, Beagle AI64).
As differentiation is done based on board, every one of these boards
would have to have checks added for them. Instead let's split J7200
support out from J721e like how normal new SoC support is done.

This patch touches several subsystems and could not be split much better
as when we add SOC_K3_J7200 we want to make use of it in all spots that
once used the combined SOC_K3_J721E so we can turn off SOC_K3_J721E when
building for J7200 boards.

Signed-off-by: Andrew Davis <afd@ti.com>