staging: udlfb: enhance EDID and mode handling support

Enhance EDID and mode table handling

* Adds support for lower-end DL chips on higher-end monitors
* Adds support for using fbdev standard EDID parsing and handling
* Adds support for more dynamic reallocation of framebuffer, based on new EDID

Queries EDID from hardware with several retries then
queries DisplayLink chip for max pixel area via vendor descriptor.
Uses existing fbdev mode handling service funcations to build mode list
of common modes between adapter and monitor.
This enables lower-end chips (e.g. DL-125) to successfully pick a compatible
mode on higher end monitors (e.g. whose default mode is over 1280x1024).
Reallocate framebuffer if necessary in response to new max mode.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>