drm/i915: Fix typo from "Enable DisplayPort Audio"

Hi,

while I looked through your changes in drm-intel git tree (as I've got
a pressure for supporting DisplayPort audio), I stumbled on the
possible bug in the commit a9756bb5

	Author: Zhenyu Wang <zhenyuw@linux.intel.com>
	Date:   Sun Sep 19 13:09:06 2010 +0800
	drm/i915: Enable DisplayPort audio

In this commit, you changed the return value of g4x_dp_detect()
to "bit", but it should be "status", I suppose.

[ickle: mea culpa.]
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31094


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>