ext_inter: remove unnecessary rate parameters

Only use compmode_interinter_cost and compmode_interintra_cost in
handle_inter_mode() since outside the function they can be reflected
by the total rate.
Plus adding config flags to separate wedge/compound_segment from
ext_inter

Change-Id: I56b402aab3cf2337bae8d7e682f93cd8557f69a4
1 file changed