soc/intel/cmn/gfx: Detect dual display (eDP + HDMI)

This patch adds support for detecting dual displays (eDP and HDMI) on
Intel platforms. This information is useful for setting the
`lb_framebuffer.has_external_display` variable, which is used to
determine whether depthchage should avoid shutting down when an
extended display is present.

TEST= Able to build and boot google/rex, where depthchage now
successfully avoids shutting down when both eDP and HDMI displays
are attached.

w/o this patch:
  with eDP and HDMI attached: .has_external_display=0
  with eDP attached: .has_external_display=0
  with HDMI attached: .has_external_display=1

w/ this patch:
  with eDP and HDMI attached: .has_external_display = 1
  with eDP attached: .has_external_display=0
  with HDMI attached: .has_external_display=1

Change-Id: Ie39d48da75a21e3508a1fbcf09da31caedaa1c0a
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78383
Reviewed-by: Eric Lai <ericllai@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions