drm/i915: Fixes distorted external screen image on HP 2730p

drm/i915: Fixes distorted external screen image on HP 2730p

Fixes LP: #796030 by removing forced pipe A on HP 2730p.  Quirk has
previously been introduced to fix a sleep mode problem that does not
exist any more.

v2: Added Tested-by and Bugzilla Link
[herton - removed Bugzilla, replaced with BugLink]

BugLink: http://bugs.launchpad.net/bugs/796030
Tested-by: Ronny Standtke <ronny.standtke@gmx.net>
Signed-off-by: Philipp Grete <mail@pgrete.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry-picked from commit d12d04512c4430e29daede7f24b97f83f8cf259a upstream)
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Acked-by: Leann Ogasawara <leann.ogasawara@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>