drm/i915: Don't check for lid presence when detecting LVDS

Checking for the presence of a lid in order to validate whether or not
an LVDS display exists fails on some development platforms that implement
a lid device but allow the LVDS to be disabled. The VBT is correctly
updated, but Linux assumes that an LVDS is still present and lies to
userspace. Remove the lid check and trust the VBT.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>