ata: libata: Add libata.force parameter max_sec

ata: libata: Add libata.force parameter max_sec

Add a new libata.force parameter called max_sec.

The parameter can take an arbitrary value using the format:
libata.force=max_sec=<number of 512B sectors>

e.g. libata.force=max_sec=8191
or
libata.force=max_sec=2048

This will allow the user to set an arbitrary maximum command size
(dev->max_sectors) using libata.force.

We cannot remove the existing libata.force parameters "max_sec_128" and
"max_sec_1024", as these are a part of the exising user facing API.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>