drm/i915/dg2: Wait for SNPS PHY calibration during display init

Initialization of the PHY is handled by the hardware/firmware, but the
driver should wait up to 25ms for the PHY to report that its calibration
has completed.

Bspec: 49189
Bspec: 50107
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723174239.1551352-28-matthew.d.roper@intel.com