mtd: nand: gpmi: fix compile error caused by pinctrl call

Fix following compile error caused by commit 39febc01 (mtd: nand: gpmi:
adopt pinctrl support).

  CC      drivers/mtd/nand/gpmi-nand/gpmi-nand.o
drivers/mtd/nand/gpmi-nand/gpmi-nand.c: In function ‘acquire_resources’:
drivers/mtd/nand/gpmi-nand/gpmi-nand.c:499:45: error: ‘pdev’ undeclared (first use in this function)

Reported-by: Subodh Nijsure <snijsure@grid-net.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>