[Oneiric] SRU: fix the math in intel_dp_link_required

[Herton R. Krzesinski]

SRU Justification

Impact
Unable to achieve some resolutions through display port because of
driver miscalculation, or sub-optimal number of links x data rate
chosen.

Fix
upstream commit cd9dde44f47501394b9f0715b6a36a92aa74c0d0

Testcase
Try attach something to display port using a resolution which should be
supported by the hardware but isn't by the driver, or enable relevant
debug and watch dmesg for sub-optimal links x data rate chosen (eg.:
http://permalink.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/6397)

-- 
[]'s
Herton