Documentation/amdgpu: Fix duplicate declaration

Address the below kernel doc warning:

Documentation/gpu/amdgpu/display/display-manager:134:
drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:3: WARNING: Duplicate C
declaration, also defined at gpu/amdgpu/display/dcn-blocks:101.
Declaration is '.. c:struct:: mpcc_blnd_cfg'.
Documentation/gpu/amdgpu/display/display-manager:146:
drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h:3: WARNING: Duplicate C
declaration, also defined at gpu/amdgpu/display/dcn-blocks:3.
Declaration is '.. c:enum:: mpcc_alpha_blend_mode'.

To address the above warnings, this commit uses the 'no-identifiers'
option in the dcn-blocks to avoid duplication with the previous use of
this function doc in the display-manager file. Finally, replaces the
deprecated ':function:' in favor of ':identifiers:'.

Cc: Alex Deucher <[email protected]>
Acked-by: Alex Deucher <[email protected]>
Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Rodrigo Siqueira <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: Rodrigo Siqueira

Documentation/gpu/amdgpu/display/dcn-blocks.rst

@@ -34,6 +34,7 @@ MPC
 
 .. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
    :internal:
+   :no-identifiers: mpcc_blnd_cfg mpcc_alpha_blend_mode
 
 OPP
 ---

Documentation/gpu/amdgpu/display/display-manager.rst

@@ -132,7 +132,7 @@ The DRM blend mode and its elements are then mapped by AMDGPU display manager
 (MPC), as follows:
 
 .. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
-   :functions: mpcc_blnd_cfg
+   :identifiers: mpcc_blnd_cfg
 
 Therefore, the blending configuration for a single MPCC instance on the MPC
 tree is defined by :c:type:`mpcc_blnd_cfg`, where
@@ -144,7 +144,7 @@ alpha and plane alpha values. It sets one of the three modes for
 :c:type:`MPCC_ALPHA_BLND_MODE`, as described below.
 
 .. kernel-doc:: drivers/gpu/drm/amd/display/dc/inc/hw/mpc.h
-   :functions: mpcc_alpha_blend_mode
+   :identifiers: mpcc_alpha_blend_mode
 
 DM then maps the elements of `enum mpcc_alpha_blend_mode` to those in the DRM
 blend formula, as follows: