drm/i915: Set crtc_state->lane_count for HDMI

Set the lane count for HDMI to 4. This will make it easier to
unduplicate CHV phy code.

This also fixes the the soft reset programming for HDMI with CHV. After
commit a8f327fb ("drm/i915: Clean up CHV lane soft reset
programming"), it wouldn't set the right bits for PCS23 since it relied
on a lane count that was never set.

v2: Set lane_count in *_get_config() to please state checker. (0day)
v3: Set lane_count for DDI in DVI mode too. (CI)
v4: Add note about CHV soft lane reset. (Ander)

Fixes: a8f327fb

 ("drm/i915: Clean up CHV lane soft reset programming")
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Jim Bride <jim.bride@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461761065-21195-2-git-send-email-ander.conselvan.de.oliveira@intel.com