drm/amd/display: Delete dead code in command_table_helper

[Why]
dig_encoder_sel_to_atom will always return zero on any ASIC version
past DCE80 since programming of the FE selection is handled by
driver, but the translation code was left in the function, making
it look like a coding error.

[How]
Remove code that has no effect, and replace with a comment describing
why it returns zero.

Signed-off-by: Julian Parkin <julian.parkin@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>

amdgpu/dc: fix non-ansi function decls.

smatch reported:
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce80/command_table_helper_dce80.c:351:71: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce80_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce110/command_table_helper_dce110.c:361:72: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce110_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce112/command_table_helper_dce112.c:415:72: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce112_get_table'
drivers/gpu/drm/amd/amdgpu/../display/dc/bios/dce112/command_table_helper2_dce112.c:415:73: warning: non-ANSI function declaration of function 'dal_cmd_tbl_helper_dce112_get_table2'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_surface.c:148:34: warning: non-ANSI function declaration of function 'dc_create_gamma'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_surface.c:178:50: warning: non-ANSI function declaration of function 'dc_create_transfer_func'

This fixes them.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Fix bugs causing Hawaii and Bonaire not light up.

Signed-off-by: Zeyu Fan <Zeyu.Fan@amd.com>
Acked-by: Jordan Lazare <Jordan.Lazare@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/dc: Add dc display driver (v2)

Supported DCE versions: 8.0, 10.0, 11.0, 11.2

v2: rebase against 4.11

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>