drm/amd/display: extend EDID support to 1kb

[why]
There exist displays with EDIDs > 512 bytes, existing code
will cause us to ignore all extension blocks.

Signed-off-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>