ARM: dts: stm32: Add usbphyc_port1 supply on DHCOM SoM

The port is unused, but shares the same supply with port0, so fill the
DT property in. This fixes the following dtbs_check warning:
arch/arm/boot/dts/stm32mp153c-dhcom-drc02.dt.yaml: usbphyc@5a006000: usb-phy@1: 'phy-supply' is a required property

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Cc: kernel@dh-electronics.com
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>