ARM: dts: qcom: msm8974: clean up USB nodes

Rename "otg" label to "usb" to group it with other usb nodes and also
because "usb" makes more sense for a USB controller.

And now we can also better use the usb_hsX_phy labels instead of having
the ulpi -> phy@X structure in every dts.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221128171623.825572-1-luca@z3ntu.xyz