drm/i915/mtl: Reset only one lane in case of MFD

In case when only two or less transmit lanes are owned such as MFD
(DP-alt with x2 lanes) we need to reset only one data lane (lane0).
With only x2 lanes we don't need to poll for the phy current
status on both data lanes since only the owned data lane will respond.

v2: Find better naming for lanes and revise the commit message (Luca)

Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com> (v1)
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Luca Coelho <luciano.coelho@intel.com> (v2)
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230601101314.332392-1-mika.kahola@intel.com