loopfilter_16_msa: fix duplicate function name

with the rename in:
1dbe80bc Unify loopfilter function names

the first instance of aom_lpf_horizontal_16_dual_msa was shadowed.
rename this instance and make it private as was done in libvpx.

Change-Id: Ifadae6850c2b7c49ee8f4c988835464ecb3bde94

aom_dsp/mips/loopfilter_16_msa.c

@@ -404,10 +404,11 @@ void aom_hz_lpf_t16_16w(uint8_t *src, int32_t pitch, uint8_t *filter48) {
   }
 }
 
-void aom_lpf_horizontal_16_dual_msa(uint8_t *src, int32_t pitch,
-                                    const uint8_t *b_limit_ptr,
-                                    const uint8_t *limit_ptr,
-                                    const uint8_t *thresh_ptr, int32_t count) {
+static void mb_lpf_horizontal_edge_dual(uint8_t *src, int32_t pitch,
+                                        const uint8_t *b_limit_ptr,
+                                        const uint8_t *limit_ptr,
+                                        const uint8_t *thresh_ptr,
+                                        int32_t count) {
   DECLARE_ALIGNED(32, uint8_t, filter48[16 * 8]);
   uint8_t early_exit = 0;
 
@@ -639,8 +640,8 @@ static void mb_lpf_horizontal_edge(uint8_t *src, int32_t pitch,
       }
     }
   } else {
-    aom_lpf_horizontal_16_dual_msa(src, pitch, b_limit_ptr, limit_ptr,
-                                   thresh_ptr, count);
+    mb_lpf_horizontal_edge_dual(src, pitch, b_limit_ptr, limit_ptr, thresh_ptr,
+                                count);
   }
 }