sata_sil: Fix build breakage

Commit e57db7bd

 (SATA Sil: Blacklist system that spins off disks during ACPI power off)
 breaks build like the following, in both cases when CONFIG_DMI set or not.

        drivers/ata/sata_sil.c: In function 'sil_broken_system_poweroff':
        drivers/ata/sata_sil.c:713: error: implicit declaration of function 'dmi_first_match'
        drivers/ata/sata_sil.c:713: warning: initialization makes pointer from integer without a cast

  sata_sil.c should include dmi.h

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>