mtd: rawnand: ingenic: Rename jz4780_bch_init to jz4780_bch_reset

The jz4780_bch_init name was confusing, as it suggested that its content
should be executed once at init time, whereas what the function really
does is reset the hardware for a new ECC operation.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>