Revert "Revert "Jit64: Fix immediates being zero-extended to cr_val inst...

Reverts dolphin-emu/dolphin#730

Turns out the regression wasn't due to that PR, so that is still a potentially valid fix. konpie did some testing showing a few other bugs as being fixed in https://code.google.com/p/dolphin-emu/issues/detail?id=7538