From: Stuart Hayes <Stuart_Hayes@dell.com>

The system can panic with a null pointer dereference using ide-scsi if
PIO is being done on scatter gather pages that are in high memory,
because page_address() returns 0.  We are actually seeing this using a
tape drive.  This patch will kmap_atomic() the pages before performing
PIO.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@elka.pw.edu.pl>