mtd: rawnand: fsl_elbc: Cosmetic move

Move the fsl_elbc_attach_chip function after the definitions of
fsl_elbc_read_page and friends in preparation for the next patch.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>