drm/i915/ddi: Make all the PORT_WIDTH macros work the same way

Make the PORT_WIDTH macro of the XELPDP_PORT_CTL1 register work the same
way as those used for the DDI_BUF_CTL and the TRANS_DDI_FUNC_CTL
registers: accept a width parameter and convert it to the given
register's encoding.

v2: Robustify macro calls with parens. (Jani)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214142001.552916-4-imre.deak@intel.com