Fix two failed case after enabling msa optimization.
Fix two failed case after enabling msa optimization.

Failed case: LibYUVConvertTest.TestI400 and LibYUVPlanarTest.ARGBBlend_Unattenuated.
This patch updates the I400ToARGBRow_MSA and ARGBBlendRow_MSA functions in the row_msa.cc file.

Signed-off-by: Shiyou Yin <95ebe55dade5ae654e1969116435bcdcabc15f88@loongson.cn>
Change-Id: Iec1a647af79be3ca1f2724802f6698deab60eac8
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/2330807
Reviewed-by: Frank Barchard <52415189a3f67d375195cbbb6fdb1f1759498e57@chromium.org>
Commit-Queue: Frank Barchard <52415189a3f67d375195cbbb6fdb1f1759498e57@chromium.org>

lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv