mtd: rawnand: marvell: ensure timing values are written

When new timing values are calculated in marvell_nfc_setup_interface()
ensure that they will be applied in marvell_nfc_select_target() by
clearing the selected_chip pointer.

Fixes: b2525141 ("mtd: rawnand: marvell: Stop implementing ->select_chip()")
Suggested-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230525003154.2303012-1-chris.packham@alliedtelesis.co.nz