We were checking that the previous instruction doesn't write flags,
but we also need to check it doesn't read them.
Fixes: 1784dd22a3 ('broadcom/compiler: pipeline smooth ldvary sequences')
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9431>