mtd: rawnand: gpmi: don't leak PM reference in error path

If gpmi_nfc_apply_timings() fails, the PM runtime usage counter must be
dropped.

Reported-by: Pavel Machek <pavel@denx.de>
Fixes: f53d4c10 ("mtd: rawnand: gpmi: Add ERR007117 protection for nfc_apply_timings")
Signed-off-by: Christian Eggers <ceggers@arri.de>
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220125081619.6286-1-ceggers@arri.de