drm/edid: support CEA video modes.

TFT/plasma televisions and projectors have become commonplace, and so
has the use of PCs to drive them. Add the video modes specified by an
EDID's CEA extension to the mode database for a connector.

Before:
[    1.158869] [drm:drm_mode_debug_printmodeline], Modeline
19:"1920x1080i" 0 74250 1920 2448 2492 2640 1080 1084 1094 1125 0x40 0x15
[    1.158875] [drm:drm_mode_debug_printmodeline], Modeline
18:"1920x1080i" 0 74250 1920 2008 2052 2200 1080 1084 1094 1125 0x48 0x15
[    1.158882] [drm:drm_mode_debug_printmodeline], Modeline
20:"1920x1080" 24 74250 1920 2558 2602 2750 1080 1084 1089 1125 0x40 0x5

After:
[    1.144175] [drm:drm_mode_debug_printmodeline], Modeline
22:"1920x1080" 0 74250 1920 2448 2492 2640 1080 1084 1094 1125 0x40 0x15
[    1.144179] [drm:drm_mode_debug_printmodeline], Modeline
21:"1920x1080" 0 74250 1920 2008 2052 2200 1080 1084 1094 1125 0x48 0x15
[    1.144187] [drm:drm_mode_debug_printmodeline], Modeline
30:"1920x1080" 50 148500 1920 2448 2492 2640 1080 1084 1089 1125 0x40 0x5
[    1.144190] [drm:drm_mode_debug_printmodeline], Modeline
29:"1920x1080" 60 148500 1920 2008 2052 2200 1080 1084 1089 1125 0x40 0x5
[    1.144192] [drm:drm_mode_debug_printmodeline], Modeline
25:"1920x1080" 24 74250 1920 2558 2602 2750 1080 1084 1089 1125 0x40 0x5
[    1.144195] [drm:drm_mode_debug_printmodeline], Modeline
24:"1280x720" 50 74250 1280 1720 1760 1980 720 725 730 750 0x40 0x5
[    1.144198] [drm:drm_mode_debug_printmodeline], Modeline
23:"1280x720" 60 74250 1280 1390 1430 1650 720 725 730 750 0x40 0x5
[    1.144201] [drm:drm_mode_debug_printmodeline], Modeline 27:"720x576"
50 27000 720 732 796 864 576 581 586 625 0x40 0xa
[    1.144203] [drm:drm_mode_debug_printmodeline], Modeline 26:"720x480"
60 27000 720 736 798 858 480 489 495 525 0x40 0xa
[    1.144206] [drm:drm_mode_debug_printmodeline], Modeline 28:"640x480"
60 25175 640 656 752 800 480 490 492 525 0x40 0xa

Signed-off-by: Christian Schmidt <schmidt@digadd.de>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>