arm64: dts: ti: k3-am68-sk-base-board: Add pinmux for RPi Header

Add pinmux required to bring out the i2c and gpios on 40-pin RPi
expansion header on the AM68 SK board.

Signed-off-by: Sinthu Raja <sinthu.raja@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Udit Kumar <u-kumar1@ti.com>
Link: https://lore.kernel.org/r/20230602153554.1571128-3-nm@ti.com


Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>