dt-bindings: phy: cadence-torrent: enable PHY_TYPE_USXGMII

dt-bindings: phy: cadence-torrent: enable PHY_TYPE_USXGMII

The Cadence Torrent SERDES supports USXGMII protocol. Hence, update the
bindings to allow PHY_TYPE_USXGMII. Since PHY_TYPE_USXGMII has the value
of "12" while the existing maximum allowed PHY TYPE is "9", switch back to
using "enum" property in the bindings to account for this discontinuity.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250411055743.623135-1-s-vadapalli@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>