arm64: dts: ti: k3-am65: Add clocks to dwc3 nodes

The TI sci-clk driver can scan the DT for all clocks provided by system
firmware and does this by checking the clocks property of all nodes, so
we must add this to the dwc3 nodes so USB clocks are available.

Without this USB does not work with latest system firmware i.e.
[    1.714662] clk: couldn't get parent clock 0 for /interconnect@100000/dwc3@4020000

Fixes: cc54a994 ("arm64: dts: ti: k3-am6: add USB suppor")
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Cc: stable@kernel.org
Signed-off-by: Tero Kristo <t-kristo@ti.com>