avcodec/ppc/hevcdsp: Fix build failures with powerpc-linux-gnu-gcc-4.8 with --disable-optimizations

The affected functions could also be changed into macros, this is the
smaller change to fix it though. And avoids (probably) less readable macros
The extra code should be optimized out when optimizations are done as all values
are known at build after inlining.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/ppc/hevcdsp.c

@@ -58,7 +58,13 @@ static av_always_inline void transform4x4(vec_s16 src_01, vec_s16 src_23,
     e1 = vec_msums(src_02, trans4[2], zero);
     o1 = vec_msums(src_13, trans4[3], zero);
 
-    add = vec_sl(vec_splat_s32(1), vec_splat_u32(shift - 1));
+    switch(shift) {
+    case  7: add = vec_sl(vec_splat_s32(1), vec_splat_u32( 7 - 1)); break;
+    case 10: add = vec_sl(vec_splat_s32(1), vec_splat_u32(10 - 1)); break;
+    case 12: add = vec_sl(vec_splat_s32(1), vec_splat_u32(12 - 1)); break;
+    default: abort();
+    }
+
     e0 = vec_add(e0, add);
     e1 = vec_add(e1, add);
 
@@ -72,7 +78,14 @@ static av_always_inline void scale(vec_s32 res[4], vec_s16 res_packed[2],
                                    const int shift)
 {
     int i;
-    vec_u32 v_shift = vec_splat_u32(shift);
+    vec_u32 v_shift;
+
+    switch(shift) {
+    case  7: v_shift = vec_splat_u32(7) ; break;
+    case 10: v_shift = vec_splat_u32(10); break;
+    case 12: v_shift = vec_splat_u32(12); break;
+    default: abort();
+    }
 
     for (i = 0; i < 4; i++)
         res[i] = vec_sra(res[i], v_shift);