Adding linux-image-extra to the depends package list of ubuntu trusty

In trusty, linux-image-generic package is split into linux-image and
linux-image-extra, ‘igb’ and display drivers are moved under extra package.

Change-Id: I991ca618b15f85104810e3c7ed0d4e639c5364cc
Merge "Adding linux-image-extra to the depends package list of ubuntu trusty"