mtd: rawnand: brcmnand: Support write protection setting from dts

The write protection feature is controlled by the module parameter wp_on
with default set to enabled. But not all the board use this feature
especially in BCMBCA broadband board. And module parameter is not
sufficient as different board can have different option.  Add a device
tree property and allow this feature to be configured through the board
dts on per board basis.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Kamal Dasu <kamal.dasu@broadcom.com>
Reviewed-by: David Regan <dregan@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240223034758.13753-14-william.zhang@broadcom.com