phy: meson8b-usb2: request a shared reset line

Both PHYs are sharing one reset line. With recent improvements to the
reset framework we can now also use reset_control_reset with shared
resets.
This allows us to drop some workarounds where the reset was only
specified for one PHY but not the other, to make sure that the reset it
only executed once (as the reset framework was not able to use
reset_control_reset with shared reset lines).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>