dt-bindings: phy: rename transmit-amplitude.yaml to phy-common-props.yaml

dt-bindings: phy: rename transmit-amplitude.yaml to phy-common-props.yaml

I would like to add more properties similar to tx-p2p-microvolt, and I
don't think it makes sense to create one schema for each such property
(transmit-amplitude.yaml, lane-polarity.yaml, transmit-equalization.yaml
etc).

Instead, let's rename to phy-common-props.yaml, which makes it a more
adequate host schema for all the above properties.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260111093940.975359-2-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>