dts: arm: nxp_kw2xd: Add SPI0 sip pins

As the KW2XD is a SiP (System-in-package) the SPI1 controller on the MCU
is connected to the modem.  As the pinctrl details for this in the
SoC dtsi file as these pins are not exposed in the pindata XMLs from
NXP.

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