LIBYUV_SSSE3_ONLY was for functions that have SSE2 and SSSE3 but are compiling for SSSE3, so SSE2 will never be used.
Remove the SSE2 implementation of ARGBSHUFFLEROW_SSE2 and rely on SSSE3.

Bug: libyuv: 769
Test: ~/intelsde/sde -p4 -- out/Release/libyuv_unittest --gtest_filter=LibYUVConvertTest.ARGBToABGR_Opt
Change-Id: I7443f4d8ee3c6f47edd2cf1d5a1eb0f8d7a1eeeb
Reviewed-on: https://chromium-review.googlesource.com/846541Reviewed-by: Weiyong Yao <braveyao@chromium.org>
Reviewed-by: Frank Barchard <fbarchard@chromium.org>