[tilegx] Shouldn't restrict BEQZ or BNEZ in PatchBranchIntoNop/PatchNopIntoBranch.

  The instruction sequences could be either BEQZ or BNEZ for both cases.
[tilegx] Fix structure type return value ABI issue.

  For TileGX, if the structure type size is < 80, we still return value
by registers. Thus, there is no need to pass a implicitly r0 which contains
pre-allocated stack space.

  this fix cut off about 100 failures.