ide_in_drive_list(): accept NULL as the wildcard for firmware revision

Earlier, the matching of (model,rev) in ide-dma black/white list
handling was to consider "ALL" in the table to match any
revision.  This makes NULL to be also an accepted wildcard, and
changes the entries of tables in ide-dma.c to use NULL.

The code still accepts "ALL" as the wildcard, in order to keep
any out-of-tree ide driver that feeds its own table that uses
"ALL" as the wildcard to ide_in_drive_list() function from
breaking.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>