avcodec/mips: Improve hevc uni-w horiz mc msa functions

Load the specific destination bytes instead of MSA load and pack.
Pack the data to half word before clipping.
Use immediate unsigned saturation for clip to max saving one vector register.
Signed-off-by: Kaustubh Raste <kaustubh.raste@imgtec.com>
Reviewed-by: Manojkumar Bhosale <Manojkumar.Bhosale@imgtec.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mips/hevc_macros_msa.h

 /*
- * Copyright (c) 2015 Manojkumar Bhosale (Manojkumar.Bhosale@imgtec.com)
+ * Copyright (c) 2015 - 2017 Manojkumar Bhosale (Manojkumar.Bhosale@imgtec.com)
  *
  * This file is part of FFmpeg.
  *
@@ -58,6 +58,17 @@
     out2 = (v4i32) __msa_pckev_b((v16i8) tmp5_m, (v16i8) tmp4_m);  \
 }
 
+#define HEVC_FILT_8TAP_SH(in0, in1, in2, in3,                    \
+                          filt0, filt1, filt2, filt3)            \
+( {                                                              \
+    v8i16 out_m;                                                 \
+                                                                 \
+    out_m = __msa_dotp_s_h((v16i8) in0, (v16i8) filt0);          \
+    out_m = __msa_dpadd_s_h(out_m, (v16i8) in1, (v16i8) filt1);  \
+    DPADD_SB2_SH(in2, in3, filt2, filt3, out_m, out_m);          \
+    out_m;                                                       \
+} )
+
 #define HEVC_FILT_8TAP(in0, in1, in2, in3,                       \
                        filt0, filt1, filt2, filt3)               \
 ( {                                                              \