[PATCH] libata: implement ata_dev_absent()

For the time being we cannot use ata_dev_present() as it was renamed
to ata_dev_enabled() but we still need presence test.  Implement
negation of the test.  Conveniently, the negated result is needed in
more places.  This is suggested by Jeff Garzik.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

include/linux/libata.h

@@ -682,6 +682,11 @@ static inline unsigned int ata_class_disabled(unsigned int class)
 	return class == ATA_DEV_ATA_UNSUP || class == ATA_DEV_ATAPI_UNSUP;
 }
 
+static inline unsigned int ata_class_absent(unsigned int class)
+{
+	return !ata_class_enabled(class) && !ata_class_disabled(class);
+}
+
 static inline unsigned int ata_dev_enabled(const struct ata_device *dev)
 {
 	return ata_class_enabled(dev->class);
@@ -692,6 +697,11 @@ static inline unsigned int ata_dev_disabled(const struct ata_device *dev)
 	return ata_class_disabled(dev->class);
 }
 
+static inline unsigned int ata_dev_absent(const struct ata_device *dev)
+{
+	return ata_class_absent(dev->class);
+}
+
 static inline u8 ata_chk_status(struct ata_port *ap)
 {
 	return ap->ops->check_status(ap);