fio: allow trim operations for verify/trim workloads

fio: allow trim operations for verify/trim workloads

Fio has the ability to verify trim operations by running a verify
workload and setting the trim_percentage, trim_backlog, and
trim_verify_zero options. Some of the written blocks will then be
trimmed and then read back to see if they are zeroed out.

This patch changes fio_ro_check to allow trim operations when fio is
running a verify/trim workload.

Fixes: 196ccc44 ("fio.h: also check trim operations in fio_ro_check")
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>