drm/amd/display: correct some hdcp variable naming

[why]
In HDCP update stream config interface, some variables are named as
xxx_supported, but in fact the variable indicates whether or not xxx_enabled.
Correct the naming so it is less confusing to read the code.

Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>