drm/i915: Skip programming FIA link enable bits for MTL+

drm/i915: Skip programming FIA link enable bits for MTL+

Starting with Xe_LPD+, although FIA is still used to readout Type-C pin
assignment, part of Type-C support is moved to PICA and programming
PORT_TX_DFLEXDPMLE1(*) registers is not applicable anymore like it was
for previous display IPs (e.g. see BSpec 49190).

v2:
  - Mention Bspec 49190 as a reference of instructions for previous
    IPs. (Shekhar Chauhan)
  - s/Xe_LPDP/Xe_LPD+/ in the commit message. (Matt Roper)
  - Update commit message to be more accurate to the changes in the IP.
    (Imre Deak)

Bspec: 65750, 65448
Reviewed-by: Shekhar Chauhan <shekhar.chauhan@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240625202652.315936-1-gustavo.sousa@intel.com
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>