drm/amd/display: Use proper enums in process_channel_reply

Clang warns when one enumerated type is implicitly converted to another.

drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_aux.c:315:19: warning:
implicit conversion from enumeration type 'enum
aux_channel_operation_result' to different enumeration type 'enum
aux_transaction_reply' [-Wenum-conversion]
                reply->status = AUX_CHANNEL_OPERATION_FAILED_HPD_DISCON;
                              ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/i2caux/dce110/aux_engine_dce110.c:349:19:
warning: implicit conversion from enumeration type 'enum
aux_channel_operation_result' to different enumeration type 'enum
aux_transaction_reply' [-Wenum-conversion]
                reply->status = AUX_CHANNEL_OPERATION_FAILED_HPD_DISCON;
                              ~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The current enum is incorrect, it should be from aux_transaction_reply,
so use AUX_TRANSACTION_REPLY_HPD_DISCON.

Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>