ide: add ide_tf_read() helper

* Factor out code reading taskfile registers from ide_end_drive_cmd()
  to the new ide_tf_read() helper.

* Add IDE_TFLAG_IN_* taskfile flags to indicate the need to load
  particular IDE taskfile register in ide_tf_read().

* Update ide_end_drive_cmd() to set respective IDE_TFLAG_IN_* taksfile flags.

* Add ide_get_lba_addr() for getting LBA sector address from taskfile struct.

* Factor out code getting sector address from ide_dump_ata_status()
  to the new ide_dump_sector() function.

* Convert ide_dump_sector() to use ide_tf_read() and ide_get_lba_addr().

* Remove no longer needed ide_read_24().

The only change in functionality caused by this patch is that
ide_dump_ata_status() no longer prints "high"/"low" parts of LBA48
sector address (of course LBA48 sector address is still printed).

Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>