dt-bindings: move cache controller bindings to a cache directory

dt-bindings: move cache controller bindings to a cache directory

There's a bunch of bindings for (mostly l2) cache controllers
scattered to the four winds, move them to a common directory.
I renamed the freescale l2cache.txt file, as while that might make sense
when the parent dir is fsl, it's confusing after the move.
The two Marvell bindings have had a "marvell," prefix added to match
their compatibles.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230330173255.109731-1-conor@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>