drm/amd/display: Reduce stack size for dml31 UseMinimumDCFCLK

Use the struct display_mode_lib pointer instead of passing lots of large
arrays as parameters by value.

Addresses this warning (resulting in failure to build a RHEL debug kernel
with Werror enabled):

../drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_mode_vba_31.c: In function ‘UseMinimumDCFCLK’:
../drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_mode_vba_31.c:7478:1: warning: the frame size of 2128 bytes is larger than 2048 bytes [-Wframe-larger-than=]

NOTE: AFAICT this function previously had no observable effect, since it
only modified parameters passed by value and doesn't return anything.
Now it may modify some values in struct display_mode_lib passed in by
reference.
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Michel Dänzer <mdaenzer@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>