Enable av1_lowbd_fwd_txfm2d_4x8_sse2
Enable av1_lowbd_fwd_txfm2d_4x8_sse2

Forgot to put it in the function table.

Change-Id: I86192158f74df84fca6c4a3dbda8b01659f6c9bd

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