st: Fix MTMKPART to work with newer drives

Change the MTMKPART operation of the MTIOCTOP ioctl so that it works
also with current drives (LTO-5/6, etc.). Send a separate FORMAT MEDIUM
command if the partition mode page indicates that this is required. Use
LOAD to position the tape at the beginning of tape.

The operation is extended so that if the argument is negative, its
absolute value specifies the size of partition 0, which is the
physically first partition of the tape.

Signed-off-by: Kai Mäkisara <kai.makisara@kolumbus.fi>
Tested-by: Shane M Seymour <shane.seymour@hpe.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>