mode management changes between local and external display.

mode management changes between local and external display.

- Defining our policy of setting the FB and surface dimensions
  of frame buffer equal to local display dimensions and choosing
  panel fitting for external display when needed. This is required since
  Medfield hardware supports panel fitting only for HDMI pipe.
- Also, remove the modes selection limitations at drm during hdmi hotplug.
  During drm_fb_helper_hotplug_event, the max_width and max_height are
  reseted to the size of available framebuffer (which is equal to local
  display), and thus removes all the hdmi modes that are greater than this
  limit thus not allowing modes like 1080P to get selected for HDMI.
  Hence changed the reset logic.

Signed-off-by: Arun Kannan <arun.kannan@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>