drm/i915: Get HDR DPCD refresh timeout from VBT

drm/i915: Get HDR DPCD refresh timeout from VBT

Grab the HDR DPCD refresh timeout (time we need to wait after
writing the sourc OUI before the HDR DPCD registers are ready)
from the VBT.

Windows doesn't even seem to have any default value for this,
which is perhaps a bit weird since the VBT value is documented
as TGL+ and I thought the HDR backlight stuff might already be
used on earlier platforms. To play it safe I left the old
hardcoded 30ms default in place. Digging through some internal
stuff that seems to have been a number given by the vendor for
one particularly slow TCON. Although I did see 50ms mentioned
somewhere as well.

Let's also include the value in the debug print to ease
debugging, and toss in the customary connector id+name as well.

The TGL Thinkpad T14 I have sets this to 0 btw. So the delay
is now gone on this machine:
 [CONNECTOR:308:eDP-1] Detected Intel HDR backlight interface version 1
 [CONNECTOR:308:eDP-1] Using Intel proprietary eDP backlight controls
 [CONNECTOR:308:eDP-1] SDR backlight is controlled through PWM
 [CONNECTOR:308:eDP-1] Using native PCH PWM for backlight control (controller=0)
 [CONNECTOR:308:eDP-1] Using AUX HDR interface for backlight control (range 0..496)
 [CONNECTOR:308:eDP-1] Performing OUI wait (0 ms)

Cc: Lyude Paul <lyude@redhat.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230220164718.23117-1-ville.syrjala@linux.intel.com
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>