ARM: dts: stm32: add support for USB2514B onboard hub on stm32mp157c-ev1

Add support for USB2514B onboard hub on stm32mp157c EV1 board. The HUB
is supplied by a 3v3 PMIC regulator.

[backport from linux ad9591b01d24]
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Tested-by: Patrick Delaunay <patrick.delaunay@foss.st.com>