drivers/ide/ide-acpi.c: fix uninitialized var warning

drivers/ide/ide-acpi.c: In function 'ide_acpi_init':
drivers/ide/ide-acpi.c:175: warning: 'dev_handle' may be used uninitialized in this function

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>