arm64: dts: imx8mp: correct usb clocks

After commit cf7f3f4f ("clk: imx8mp: fix usb_root_clk parent"),
usb_root_clk is no longer for suspend clock so update dts accordingly
to use right bus clock and suspend clock.

Fixes: fb8587a2 ("arm64: dtsi: imx8mp: add usb nodes")
Cc: stable@vger.kernel.org # ed1f4ccf: clk: imx: imx8mp: add shared clk gate for usb suspend clk
Cc: stable@vger.kernel.org # v5.19+
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Li Jun <jun.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>