drm/i915/gvt: add more resolutions in virtual edid

The current virtual edid can only support the resolution up
to 1024x768. Update the virtual edid so that can support more
resoltions. With this new virtual edid, resolution can
be up to 1920x1200.

V2: add detailed modeline description in edid code comments

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>