Simplify file dependencies of SIMD implementation of interpolation filters

This is a similar change to following aom CL
https://aomedia-review.googlesource.com/#/c/1961/

Move SIMD related functions from filter.c/h to following files
av1_convolve_ssse3.c
av1_highbd_convolve_filters_sse4.c

Change following c files to header files.
av1_highbd_convolve_filters_sse4.c
av1_convolve_filters_ssse3.c

Change-Id: I41a3cc6b0789e632451aeda82f5eb97a4d78e370
9 files changed