driver/ddr/fsl: Add sync of refresh

Add sync of refresh for multiple DDR controllers. DDRC initialization
needs to complete first. Code is re-ordered to keep refresh close.

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/include/fsl_ddr.h b/include/fsl_ddr.h
index 96fde91..feccef9 100644
--- a/include/fsl_ddr.h
+++ b/include/fsl_ddr.h
@@ -118,6 +118,8 @@
 		const common_timing_params_t *memctl_common_params,
 		unsigned int memctl_interleaved,
 		unsigned int ctrl_num);
+void fsl_ddr_sync_memctl_refresh(unsigned int first_ctrl,
+				 unsigned int last_ctrl);
 
 int fsl_ddr_interactive_env_var_exists(void);
 unsigned long long fsl_ddr_interactive(fsl_ddr_info_t *pinfo, int var_is_set);