dec_neon: harmonize function suffixes
dec_neon: harmonize function suffixes

BUG=webp:355

Change-Id: I61c9a0c9e24515322955e04afd8c4ea6a44b9319

webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp