drm/amd/display: Drop unnecessary DCN guards

[Why & How]
DC is littered with many DCN guards that are not needed.
Drop them.

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: rename DCN1_0 kconfig to DCN

Since dcn20 and dcn21 are under dcn1 it doesnt make sense to
have it named dcn1.

Change it to "dcn" to make it generic

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Add DCN2 DWB

Add support to program the DCN2 DWB (Display Writeback)

HW Blocks:

+--------++------+ +----------+
| HUBBUB || HUBP | <-- | MMHUBBUB |
+--------++------+ +----------+
| ^
v |
+--------+ +--------+
| DPP | | DWB |
+--------+ +--------+
|
v ^
+--------+ |
| MPC | |
+--------+ |
| |
v |
+-------+ |
| OPP | |
+-------+ |
| |
v |
+--------+ /
| OPTC | --------------
+--------+
|
v
+--------+ +--------+
| DIO | | DCCG |
+--------+ +--------+

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Remove DWB

It's not in a good shape and currently completely unused.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: move dwb registers to header file

Signed-off-by: Yue Hin Lau <Yuehin.Lau@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: add display write back(DWB)

Signed-off-by: Duke Du <Duke.Du@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>