mtd: rawnand: brcmnand: Refactored code to introduce helper functions

[ Upstream commit 3c7c1e45

 ]

Refactored NAND ECC and CMD address configuration code to use helper
functions.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>