FPU: Round to single precision for fcfid[u]s

The fcfids and fcfidus instructions weren't rounding to single
precision because r.longmask wasn't getting set.  To fix this, set
v.longmask to e_in.single for the fcfid* instructions.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

fpu.vhdl

@@ -1185,6 +1185,7 @@ begin
                             end if;
                         when "10110" =>        -- fcfid
                             v.result_sign := e_in.frb(63);
+                            v.longmask := e_in.single;
                         when others =>
                             v.result_sign := '0';
                     end case;