mtd: rawnand: brcmnand: Fix ECC level field setting for v7.2 controller

v7.2 controller has different ECC level field size and shift in the acc
control register than its predecessor and successor controller. It needs
to be set specifically.

Fixes: decba6d4

 ("mtd: brcmnand: Add v7.2 controller support")
Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230706182909.79151-2-william.zhang@broadcom.com