arm64: dts: ti: am6-main: Add gpio nodes

Add gpio0/1 nodes under main domain. They have 96 and 90 gpios
respectively and all are capable of generating banked interrupts.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>