drm/amd/display: Remove unused dcn_find_dcfclk_suits_all

dcn_find_dcfclk_suits_all() last use was removed by 2018's
commit 4fd994c4 ("drm/amd/display: Start using the new pp_smu
interface")

Remove it, and the dcn_find_normalized_clock_vdd_Level helper it used.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>