[libata] Kconfig: Elaborate that SFF is meant for legacy and PATA stuff

Building Linux for an ASUS Eee PC 701 4G with

        ata2.00: CFA: SILICONMOTION SM223AC, , max UDMA/66
        ata2.00: 7815024 sectors, multi 0: LBA
        ata2.00: configured for UDMA/66
        scsi 1:0:0:0: Direct-Access     ATA      SILICONMOTION SM n/a  PQ: 0 ANSI: 5
        sd 1:0:0:0: [sda] 7815024 512-byte logical blocks: (4.00 GB/3.72 GiB)
        sd 1:0:0:0: [sda] Write Protect is off
        sd 1:0:0:0: [sda] Mode Sense: 00 3a 00 00
        sd 1:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
         sda: sda1
        sd 1:0:0:0: [sda] Attached SCSI disk
        sd 1:0:0:0: Attached scsi generic sg0 type 0

I followed the advice to not use the deprecated old PATA subsystem

        ATA/ATAPI/MFM/RLL support (DEPRECATED)  --->

and use the ATA subsystem instead.

        Serial ATA and Parallel ATA drivers  --->

Unfortunately I needed several tries to find out, that I needed the SFF
menu I had not selected before because I had never heard that term
before. I think it would have helped me, to have PATA or legacy IDE in
that item’s name.

Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>