[Why]
With all DCE6 specific macros, register, masks in place
dce60_resource.c may use them and become independent from DCE8 headers

[How]
(v1) Changelog:
- use DCE6 headers for registers and masks, remove the DC8 headers
- remove 7th Display Controller/Encoder register instances (DCE6 has only 6)
- use DCE6 specific watermark programming registers (DPG_PIPE_ARBITRATION_CONTROL3)
- use DCE6 specific input pixel processing registers shift/mask
- use DCE6 specific transform registers shift/mask
- use DCE6 specific link encoder registers shift/mask
- use DCE6 specific output pixel processing registers shift/mask
- use DCE6 specific audio registers shift/mask
- use DCE6 specific dmcu registers shift/mask
- use DCE6 specific hwseq registers shift/mask
- use DCE6 specific mem input registers shift/mask

(v2) Changelog:
- use DCE6 ad hoc dce60_mem_input_construct() function
- use DCE6 ad hoc dce60_transform_construct() function

(v3) Changelog:
- use DCE6 ad hoc dce60_ipp_construct() function

(v4) Changelog:
- use DCE6 ad hoc dce60_link_encoder_construct() function

(v5) Changelog:
- use DCE6 ad hoc dce60_opp_construct() function

(v6) Changelog:
- use DCE6 ad hoc dce60_audio_create() function
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>