drm/amd/display: Fix call to pass bpp in 16ths of a bit

[Why & How?]
Call to dc_dsc_compute_bandwidth_range should have min and max bpp
in 16ths of a bit.  Multiply min and max bpp from policy.

Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Reviewed-by: Eryk Brol <Eryk.Brol@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>