Use pinctrl-0 for pinctrl_rfkill to fix the following
'make CHECK_DTBS=y imx7d-smegw01.dtb' warning:

regulator-wlan-rfkill: 'pinctrl-0' is a dependency of 'pinctrl-names'
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>