ata: make SATA_PMP option selectable only if any SATA host driver is enabled

There is no reason to expose SATA_PMP config option when no SATA
host drivers are enabled. To fix it add SATA_HOST config option,
make all SATA host drivers select it and finally make SATA_PMP
config options depend on it.

This also serves as preparation for the future changes which
optimize libata core code size on PATA only setups.

CC: "James E.J. Bottomley" <jejb@linux.ibm.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> # for SCSI bits
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>