dt-bindings: usb: dwc3: Fix usb-phy check

dt-bindings: usb: dwc3: Fix usb-phy check

The original binding was allowing any combination of usb2-phy and
usb3-phy in the phys and phy-names properties.

However, the current binding enforces that those properties must be a
list of usb2-phy and usb3-phy, with exactly one element, effectively
making usb2-phy the only value being valid.

Let's rework the properties description to allow either one or two
element picked with values either usb2-phy or usb3-phy. The rest of the
tooling makes sure that we don't get any duplicate value, so this should
be what we want.

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210927073514.14334-2-maxime@cerno.tech
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>