drm/amd/display: don't initialize result

The wrong enum type is used to initialize the result, leading to a
warning when using clang:
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link_dp.c:1998:26: warning:
      implicit conversion from enumeration type 'enum ddc_result' to different
      enumeration type 'enum dc_status' [-Wenum-conversion]
        enum dc_status result = DDC_RESULT_UNKNOWN;
                       ~~~~~~   ^~~~~~~~~~~~~~~~~~
1 warning generated.

Initialization of result is unnecessary anyway, just drop the
initialization.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>