drivers/ddr/fsl_ddr: Make SR_IE configurable

SR_IE(Self-refresh interrupt enable) is needed for
Hardware Based Self-Refresh. Make it configurable and let
board code handle the rest.

Signed-off-by: Joakim Tjernlund <joakim.tjernlund@transmode.se>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/drivers/ddr/fsl/ctrl_regs.c b/drivers/ddr/fsl/ctrl_regs.c
index 8367c95..8543679 100644
--- a/drivers/ddr/fsl/ctrl_regs.c
+++ b/drivers/ddr/fsl/ctrl_regs.c
@@ -858,7 +858,7 @@
 			break;
 		}
 	}
-
+	sr_ie = popts->self_refresh_interrupt_en;
 	num_pr = 1;	/* Make this configurable */
 
 	/*