dt-bindings: mtd: brcmnand: Updates for bcmbca SoCs

Update the descriptions to reflect different families of broadband SoC and
use the general name bcmbca for ARM based SoC.

Remove the requirement of interrupts property to reflect the driver
code and only require interrupt-names when interrupts property present.

Also add myself to the list of maintainers.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: David Regan <dregan@broadcom.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240223034758.13753-5-william.zhang@broadcom.com