mtd: rawnand: brcmnand: propagate init error -EPROBE_DEFER up

MTD subsystem may return -EPROBE_DEFER if something isn't ready yet.
It's important to pass that error up so device will get probed later.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Acked-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230719084324.14799-1-zajec5@gmail.com