graphics_driver: only 0300 VIDEO class can be detected

[Po-Hsu Lin]

For display controllers, there are 4 kinds of them [1]:
0300 VGA compatible controller
0301 XGA compatible controller
0302 3D controller
0380 Display controller

But our graphics_driver script only parse 0300 for video controllers.
Which would causes a false-positive hybrid_graphics_check result
if the system comes with a 0300, and another 03XX video controller.

[1] http://pci-ids.ucw.cz/read/PD/03