drm/amd/display: Increase Max EDID Size Constant

[HOW & WHY]
Change max EDID size constant to 1280 to support
10-block EDIDs.

Signed-off-by: Aidan Gratton <Aidan.Gratton@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>