dts: st: stm32u595: remove OTGHSPHY enable bit from usbotg_hs clocks

37bdc38e failed to take into account commit
f72ef5c2, and added the OTGHSPHYEN bit
back into the OTGHS controller's `clocks` property. This should have no
functional impact (due to how the USB driver is implemented), but ought
to be removed anyways as duplicates information and is confusing.

Clean the DTSI for U595 and revert back OTGHS controller `clocks` such
that it only contain the controller's clock enable bit, as it should.

Signed-off-by: Mathieu Choplain <mathieu.choplain@st.com>