mtd: rawnand: brcmnand: exec_op helper functions return type fixes

Fix return types for exec_op reset and status helper functions.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: http://lists.infradead.org/pipermail/linux-mtd/2023-December/102423.html
Fixes: 3c8260ce

 ("mtd: rawnand: brcmnand: exec_op implementation")
Signed-off-by: David Regan <dregan@broadcom.com>
Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240223034758.13753-2-william.zhang@broadcom.com