If both breaks are in the else branch, we have to use iand.
Fixes: 9995f33 ("nir: add merge loop terminators optimisation")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/11726
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30850>