ddr: Remove <common.h> and add needed includes

Remove <common.h> from this driver directory and when needed
add missing include files directly.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/ddr/fsl/ddr4_dimm_params.c b/drivers/ddr/fsl/ddr4_dimm_params.c
index ea79162..75e3bfe 100644
--- a/drivers/ddr/fsl/ddr4_dimm_params.c
+++ b/drivers/ddr/fsl/ddr4_dimm_params.c
@@ -10,10 +10,10 @@
  *
  */
 
-#include <common.h>
 #include <fsl_ddr_sdram.h>
 #include <log.h>
 #include <linux/bug.h>
+#include <linux/string.h>
 
 #include <fsl_ddr.h>