ZTS: Fix trim/trim_config and trim/autotrim_config

ZTS: Fix trim/trim_config and trim/autotrim_config

There have been occasional CI failures which occur when the trimmed
vdev size exactly matches the target size.  Resolve this by slightly
relaxing the conditional and checking for -ge rather than -gt.  In
all of the cases observer, the values match exactly.  For example:

    Failure /mnt/trim-vdev1 is 768 MB which is not -gt than 768 MB

Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #9399