mtd: rawnand: gpmi: Uninline the gpmi_check_ecc function

The gpmi_check_ecc() is not small after adding more strict ecc check,
uninline it.

Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220412025246.24269-4-han.xu@nxp.com