drm/i915/dpio: Rename a few CHV DPIO PHY registers

drm/i915/dpio: Rename a few CHV DPIO PHY registers

Drop the leading underscore from the CHV PHY common lane
register definitions. We use these directly from actual
code so the underscore here is misleading as usually it indicates
an intermediate define that shouldn't be used directly.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240422083457.23815-12-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>