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

 drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c: In function ‘calculate_bandwidth’:
 drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c:109:18: warning: variable ‘v_filter_init_mode’ set but not used [-Wunused-but-set-variable]
 drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c: In function ‘bw_calcs’:
 drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dce_calcs.c:3031:21: warning: variable ‘sclk_lvl’ set but not used [-Wunused-but-set-variable]

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>