piix: remove stale comments

 *

 *  May be copied or modified under the terms of the GNU General Public License

 *

 *  PIO mode setting function for Intel chipsets.

 *  For use instead of BIOS settings.

 * Documentation:

 *

 * 40-41

 * 42-43

 * 

 *                 41

 *                 43

 *

 * | PIO 0       | c0 | 80 | 0 |

 * | PIO 2 | SW2 | d0 | 90 | 4 |

 * | PIO 3 | MW1 | e1 | a1 | 9 |

 * | PIO 4 | MW2 | e3 | a3 | b |

 *

 * sitre = word40 & 0x4000; primary

 * sitre = word42 & 0x4000; secondary

 *

 * 44 8421|8421    hdd|hdb

 *

 * 48 8421         hdd|hdc|hdb|hda udma enabled

 *

 *    0001         hda

 *    0010         hdb

 *    0100         hdc

 *    1000         hdd

 *

 * 4a 84|21        hdb|hda

 * 4b 84|21        hdd|hdc

 *

 *    ata-33/82371AB

 *    ata-33/82371EB

 *    ata-33/82801AB            ata-66/82801AA

 *    00|00 udma 0              00|00 reserved

 *    01|01 udma 1              01|01 udma 3

 *    10|10 udma 2              10|10 udma 4

 *    11|11 reserved            11|11 reserved

 *

 * 54 8421|8421    ata66 drive|ata66 enable

 *

 * pci_read_config_word(HWIF(drive)->pci_dev, 0x40, &reg40);

 * pci_read_config_word(HWIF(drive)->pci_dev, 0x42, &reg42);

 * pci_read_config_word(HWIF(drive)->pci_dev, 0x44, &reg44);

 * pci_read_config_byte(HWIF(drive)->pci_dev, 0x48, &reg48);

 * pci_read_config_word(HWIF(drive)->pci_dev, 0x4a, &reg4a);

 * pci_read_config_byte(HWIF(drive)->pci_dev, 0x54, &reg54);

 *

 * Documentation

 *	Publically available from Intel web site. Errata documentation

 * is also publically available. As an aide to anyone hacking on this

 * driver the list of errata that are relevant is below.going back to