This change makes the c match the assembly and removes the todo's
associated with getting this to work.
Change-Id: Ie32e9ebb584a9d60399662d8bcb71b74fbd19d1e
In so doing this fixes a couple of bugs:
vpx_plane_add_noise.c needed to subtract a clamp instead of add.
And the assembly (mmx sse) had assumptions that parameters were
continuous in memory which was not true.
Change-Id: I76f2c43cf54bfc838eb2edf8a443eaaa7565d7b5
