dt-bindings: mtd: brcmnand: convert to the json-schema

This helps validating DTS files.

Changes that require mentioning:
1. Property "clock" was renamed to "clocks"
2. Duplicated properties (defined in nand-controller.yaml) were dropped
3. Compatible "brcm,nand-bcm63168" was added
4. SoC specific "compatible" cases got limited controller versions

Examples changes:
1. Nodes "nand" were renamed to "nand-controller"
2. Nodes "nandcs" were renamed to "nand"
3. Dropped partitions as they were using old syntax and are well
   documented elsewhere anyway

This rewritten binding validates cleanly using the "dt_binding_check".
Some Linux stored DTS files will require updating to make "dtbs_check"
happy.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210423050536.29504-1-zajec5@gmail.com