arm64: dts: ti: k3-am64-main: Add PCIe DT node

AM64 has one PCIe instance which can be configured in either
host mode (RC) or device mode (EP). Add PCIe DT node for host
mode and device mode here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210603142251.14563-3-kishon@ti.com