drivers/ddr/fsl: Update fsl_ddr_board_options as weak function

fsl_ddr_board_options is generally defined in board
board's ddr.c, but some boards like lx2160ardb board
does not need this function.
Defining fsl_ddr_board_options as weak function to
resolve compilation errors for such boards.

Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
[PK: Fix checkpatch warnings]
Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/drivers/ddr/fsl/options.c b/drivers/ddr/fsl/options.c
index 7639a8b..4573ffa 100644
--- a/drivers/ddr/fsl/options.c
+++ b/drivers/ddr/fsl/options.c
@@ -22,9 +22,12 @@
  */
 
 /* Board-specific functions defined in each board's ddr.c */
-extern void fsl_ddr_board_options(memctl_options_t *popts,
-		dimm_params_t *pdimm,
-		unsigned int ctrl_num);
+void __weak fsl_ddr_board_options(memctl_options_t *popts,
+				  dimm_params_t *pdimm,
+				  unsigned int ctrl_num)
+{
+	return;
+}
 
 struct dynamic_odt {
 	unsigned int odt_rd_cfg;