imx8qm_mek: Remove unused function detail_board_ddr_info()

detail_board_ddr_info() is not used anywhere, so simply remove it.

This function is only used by Layerscape, not by i.MX.

This was detected by the following sparse warning:

board/freescale/imx8qm_mek/imx8qm_mek.c:102:6: warning: no previous
prototype for ‘detail_board_ddr_info’ [-Wmissing-prototypes]
diff --git a/board/freescale/imx8qm_mek/imx8qm_mek.c b/board/freescale/imx8qm_mek/imx8qm_mek.c
index 139f416..3f6a183 100644
--- a/board/freescale/imx8qm_mek/imx8qm_mek.c
+++ b/board/freescale/imx8qm_mek/imx8qm_mek.c
@@ -100,11 +100,6 @@
 	return 0;
 }
 
-void detail_board_ddr_info(void)
-{
-	puts("\nDDR    ");
-}
-
 /*
  * Board specific reset that is system reset.
  */