arm64: dts: ti: k3-am642-sk: Add DT entry for onboard LEDs

AM642 SK has 8 leds connected to tpic2810 onboard. Add support for these
gpio leds.

Signed-off-by: Aparna M <a-m1@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Bryan Brattlof <bb@ti.com>
Link: https://lore.kernel.org/r/20220830123254.522222-1-vigneshr@ti.com