JNT_COMP: SIMD implementation for aom_jnt_sub_pixel_avg

Change function names and add SIMD implementation for two c functions:
(1) var_filter_block2d_bil_first_pass
(2) var_filter_block2d_bil_second_pass

This CL allows aom_jnt_sub_pixel_avg_variance now in SIMD.

Change-Id: Ib41ef13d62ae91a0ca481bcebb24568dcd4722c4
diff --git a/aom_dsp/aom_dsp.cmake b/aom_dsp/aom_dsp.cmake
index 2844d6f..e3aac0d 100644
--- a/aom_dsp/aom_dsp.cmake
+++ b/aom_dsp/aom_dsp.cmake
@@ -65,7 +65,7 @@
 if (CONFIG_JNT_COMP)
   set(AOM_DSP_COMMON_INTRIN_SSSE3
       ${AOM_DSP_COMMON_INTRIN_SSSE3}
-      "${AOM_ROOT}/aom_dsp/x86/variance_ssse3.c")
+      "${AOM_ROOT}/aom_dsp/x86/jnt_variance_ssse3.c")
 endif ()
 
 set(AOM_DSP_COMMON_INTRIN_SSE4_1