Rename av1_fwd_txfm2d_sse4_1 test
Rename av1_fwd_txfm2d_sse4_1 test

Rename av1_fwd_txfm2d_{sse2,sse4_1} to
{SSE2,SSE4_1}/AV1FwdTxfm2dTest.
This could avoid the error report by valgrind.

BUG=aomedia:1756

Change-Id: I7f08247e82d5475cb53539532cda0cbd4a640203

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom