libata: remove ATA_FLAG_MMIO

Commit 0d5ff566779f894ca9937231a181eb31e4adff0e (libata: convert to iomap)
removed all checks of ATA_FLAG_MMIO but neglected to remove the flag itself.
Do it now, at last...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index 8b5ea39..a791b8ce 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -660,8 +660,7 @@
  * @dev: target ATA device
  * @gtf: raw ATA taskfile register set (0x1f1 - 0x1f7)
  *
- * Outputs ATA taskfile to standard ATA host controller using MMIO
- * or PIO as indicated by the ATA_FLAG_MMIO flag.
+ * Outputs ATA taskfile to standard ATA host controller.
  * Writes the control, feature, nsect, lbal, lbam, and lbah registers.
  * Optionally (ATA_TFLAG_LBA48) writes hob_feature, hob_nsect,
  * hob_lbal, hob_lbam, and hob_lbah.