ppc: fix vc1 inverse transform, unbreak build

GCC 4.3 and later are more particular about signedness matching
in vector operations.  The operations under if(rangered) were
missing assignments and thus had no effect.
Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 381efba0)

libavcodec/ppc/vc1dsp_altivec.c

@@ -146,7 +146,7 @@ static void vc1_inv_trans_8x8_altivec(DCTELEM block[64],
     const vector  signed int vec_1s = vec_splat_s32(1);
     const vector unsigned int vec_1 = vec_splat_u32(1);
     const vector unsigned short rangered_shift = vec_splat_u16(1);
-    const vector   signed short signed_bias = vec_sl(vec_splat_u16(4),
+    const vector   signed short signed_bias = vec_sl(vec_splat_s16(4),
                                                      vec_splat_u16(4));
 
     src0 = vec_ld(  0, block);
@@ -219,23 +219,23 @@ static void vc1_inv_trans_8x8_altivec(DCTELEM block[64],
 
     if (rangered) {
         if (!sign) {
-            vec_sub(src0, signed_bias);
-            vec_sub(src1, signed_bias);
-            vec_sub(src2, signed_bias);
-            vec_sub(src3, signed_bias);
-            vec_sub(src4, signed_bias);
-            vec_sub(src5, signed_bias);
-            vec_sub(src6, signed_bias);
-            vec_sub(src7, signed_bias);
+            src0 = vec_sub(src0, signed_bias);
+            src1 = vec_sub(src1, signed_bias);
+            src2 = vec_sub(src2, signed_bias);
+            src3 = vec_sub(src3, signed_bias);
+            src4 = vec_sub(src4, signed_bias);
+            src5 = vec_sub(src5, signed_bias);
+            src6 = vec_sub(src6, signed_bias);
+            src7 = vec_sub(src7, signed_bias);
         }
-        vec_sl(src0, rangered_shift);
-        vec_sl(src1, rangered_shift);
-        vec_sl(src2, rangered_shift);
-        vec_sl(src3, rangered_shift);
-        vec_sl(src4, rangered_shift);
-        vec_sl(src5, rangered_shift);
-        vec_sl(src6, rangered_shift);
-        vec_sl(src7, rangered_shift);
+        src0 = vec_sl(src0, rangered_shift);
+        src1 = vec_sl(src1, rangered_shift);
+        src2 = vec_sl(src2, rangered_shift);
+        src3 = vec_sl(src3, rangered_shift);
+        src4 = vec_sl(src4, rangered_shift);
+        src5 = vec_sl(src5, rangered_shift);
+        src6 = vec_sl(src6, rangered_shift);
+        src7 = vec_sl(src7, rangered_shift);
     }
 
     vec_st(src0,  0, block);