FPU: Set FPSCR[FPRF] to zero for convert to integer operations

This seems to be what P9 does.

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

fpu.vhdl

@@ -713,9 +713,13 @@ architecture behaviour of fpu is
     end;
 
     -- Determine result flags to write into the FPSCR
-    function result_flags(sign: std_ulogic; class: fp_number_class; unitbit: std_ulogic)
+    function result_flags(sign: std_ulogic; class: fp_number_class; int_result: std_ulogic;
+                          unitbit: std_ulogic)
         return std_ulogic_vector is
     begin
+        if int_result = '1' then
+            return "00000";
+        else
             case class is
                 when ZERO =>
                     return sign & "0010";
@@ -726,6 +730,7 @@ architecture behaviour of fpu is
                 when NAN =>
                     return "10001";
             end case;
+        end if;
     end;
 
 begin
@@ -3651,7 +3656,7 @@ begin
         end if;
 
         if r.update_fprf = '1' then
-            v.fpscr(FPSCR_C downto FPSCR_FU) := result_flags(r.res_sign, r.result_class,
+            v.fpscr(FPSCR_C downto FPSCR_FU) := result_flags(r.res_sign, r.result_class, r.int_result,
                                                              r.r(UNIT_BIT) and not r.denorm);
         end if;