drm/amd/display/dc/link/protocols/link_dp_training: Remove set but unused variable...

drm/amd/display/dc/link/protocols/link_dp_training: Remove set but unused variable 'result'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_training.c: In function ‘perform_link_training_with_retries’:
 drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_training.c:1586:38: warning: variable ‘result’ set but not used [-Wunused-but-set-variable]

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Wenjing Liu <wenjing.liu@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>