ARM: dts: imx6-sabreauto: add pinctrl for gpt input capture

Add pinctrl groups for both GPT input capture channels.

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>