ata: Remove the AHCI_HFLAG_EDGE_IRQ support from libahci.

The flexibility to override the irq handles in the LLD's are already
present, so controllers implementing a edge trigger latch can
implement their own interrupt handler inside the driver.  This patch
removes the AHCI_HFLAG_EDGE_IRQ support from libahci and moves edge
irq handling to ahci_xgene.

tj: Minor update to description.

Signed-off-by: Suman Tripathi <stripathi@apm.com>
Signed-off-by: Tejun Heo <tj@kenrel.org>
diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index cf48e3e..167ba7e 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -240,8 +240,7 @@
 						        error-handling stage) */
 	AHCI_HFLAG_NO_DEVSLP		= (1 << 17), /* no device sleep */
 	AHCI_HFLAG_NO_FBS		= (1 << 18), /* no FBS */
-	AHCI_HFLAG_EDGE_IRQ		= (1 << 19), /* HOST_IRQ_STAT behaves as
-							Edge Triggered */
+
 #ifdef CONFIG_PCI_MSI
 	AHCI_HFLAG_MULTI_MSI		= (1 << 20), /* multiple PCI MSIs */
 	AHCI_HFLAG_MULTI_MSIX		= (1 << 21), /* per-port MSI-X */