MLK-11236 mtd: gpmi-nand: Fix nand runtime PM issue

Because of the delay of auto suspend, the nand clocks are delayed to
disable when calling the clk_set_rate. This causes the clk_set_rate
failed on some platforms like 6q/6qp, and finally lead the NAND not
working.

Signed-off-by: Ye.Li <Ye.Li@freescale.com>
Signed-off-by: Fugang Duan <B38611@freescale.com>
(cherry picked from commit: 1334dd236d4401d6635accb6c8472d8a5ed088b5)