sed-opal: add IOC_OPAL_GET_SUM_STATUS ioctl.

sed-opal: add IOC_OPAL_GET_SUM_STATUS ioctl.

This adds a function for retrieving the set of Locking objects enabled
for Single User Mode (SUM) and the value of the
RangeStartRangeLengthPolicy parameter.

It retrieves data from the LockingInfo table, specifically the
columns SingleUserModeRanges and RangeStartLengthPolicy, which
were added according to the TCG Opal Feature Set: Single User Mode,
as described in chapters 4.4.3.1 and 4.4.3.2.

Signed-off-by: Ondrej Kozina <okozina@redhat.com>
Reviewed-and-tested-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>