ARM: dts: imx53-qsb: Do not use GPIO1_8 as wakeup source

On the mx53qsb board with mc34708 PMIC, GPIO1_8 resets the system, so better not
to use it as a wakeup source.

Use GPIO 2_14 and 2_15 for wakeup sources instead.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>