[tilegx] Fix a critical bug in FullCodeGenerator::EnterFinallyBlock.

  Int->Smi conversion is wrong for TileGX.
[tilegx] Various code cleanup. No functional changes.
[tilegx] Remove some of those redundant "move r0, a0", as for TileGX,
r0 and a0 are the same registers.

  we are many other similars here and there, will remove them all after
TileGX v8 be stable.
[tilegx] Fix ABI issue in ProfileEntryHookStub::Generate.

  here, we are calling from JS to C/C++, so we need to protect the
reserved bottom 16bytes on stack, just like what we have done in
CEntryStub.
[tilegx] Fix "right operand" and "return value" collision.

  In v8, for binary operation, rhs and lhs are always kept in r0/r1,
while r0 is also used as return value. Here, we pre-set return value
in some code path, this will clobber right operand.