mtd: rawnand: vf610: disable clk on error handling path in probe

vf610_nfc_probe() does not invoke clk_disable_unprepare() on one error
handling path. The patch fixes that.

Found by Linux Driver Verification project (linuxtesting.org).

Fixes: 6f0ce4df ("mtd: rawnand: vf610: Avoid a potential NULL pointer dereference")
Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200806072634.23528-1-novikov@ispras.ru