ata_generic: Skip is_intel_ider() check when ata_generic=1 is set

When ata_generic_ide=1 is set don't do the is_intel_ider() magic
check. We found at least one box who needed that.

Cc: alan@linux.intel.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>