ARM: dts: stm32: Harmonize EHCI/OHCI DT nodes name on stm32mp15

In accordance with the Generic EHCI/OHCI bindings the corresponding node
name is suppose to comply with the Generic USB HCD DT schema, which
requires the USB nodes to have the name acceptable by the regexp:
"^usb(@.*)?" . Make sure the "generic-ehci" and "generic-ohci"-compatible
nodes are correctly named.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Acked-by: Amelie Delaunay <amelie.delaunay@st.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>