spi: brcm,spi-bcm-qspi: convert to the json-schema

This helps validating DTS files.

Changes that require mentioning:
1. reg-names
   "mspi_regs" and "bspi_regs" were renamed to "mspi" and "bspi" as that
   is what's used in DTS files and in Linux driver
2. interrupt-names
   Names were reordered. "mspi_done" has to go first as it's always
   required.
3. spi-rx-bus-width
   Property description was dropped as it's part of the
   spi-controller.yaml
4. Examples:
   * drop partitions as they are well documented elsewhere
   * regs and interrupts were formatted and reordered to match yaml
   * <0x1c> was replaced with <&gic>
   * "m25p80" node name became "flash"
   * dropped invalid "m25p,fast-read" property
   * dropped undocumented and Linux-unused "clock-names"

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

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210416194723.23855-1-zajec5@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>