drm/amd/display: Remove unused variable 'scl_enable'

Compiling AMD GPU drivers displays a warning:

drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn314/display_rq_dlg_calc_314.c: In function ‘dml_rq_dlg_get_dlg_params’:
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn314/display_rq_dlg_calc_314.c:991:14: warning: variable ‘scl_enable’ set but not used [-Wunused-but-set-variable]

Get rid of it by removing the variable 'scl_enable'.

Signed-off-by: Caio Novais <caionovais@usp.br>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>