drm/amd/display: Rename a struct field to describe a cea component better

[why]
Need to fix the code so it does not use reserved keywords

[how]
Change the total_length member of the cea struct

Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Pavle Kotarac <Pavle.Kotarac@amd.com>
Signed-off-by: Oliver Logush <oliver.logush@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>