drm/i915/xe3: Restrict PTL intel_encoder_is_c10phy() to only PHY A

drm/i915/xe3: Restrict PTL intel_encoder_is_c10phy() to only PHY A

On PTL, no combo PHY is connected to PORT B. However, PORT B can
still be used for Type-C and will utilize the C20 PHY for eDP
over Type-C. In such configurations, VBTs also enumerate PORT B.

This leads to issues where PORT B is incorrectly identified as using the
C10 PHY, due to the assumption that returning true for PORT B in
intel_encoder_is_c10phy() would not cause problems.

From PTL's perspective, only PORT A/PHY A uses the C10 PHY.

Update the helper intel_encoder_is_c10phy() to return true only for
PORT A/PHY on PTL.

v2: Change the condition code style for ptl/wcl

Bspec: 72571,73944
Fixes: 9d10de78a37f ("drm/i915/wcl: C10 phy connected to port A and B")
Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://lore.kernel.org/r/20250922150317.2334680-4-dnyaneshwar.bhadane@intel.com