dts: bindings: nxp: Add pinctrl-0 as a required property

Add pinctrl-0 as being required on NXP Kinetis DTS bindings for I2C,
FTM, UART, and DSPI related devices.

Other devices like ethernet and CAN are utilized outside of just the
Kinetis family and thus we can not require pinctrl-0 property for them
at this time.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>