Fix some new warnings found in build testing.

boards/arm/lpc17xx_40xx/lx_cpu/src/lpc17_40_bringup.c

@@ -358,6 +358,7 @@ static int nsh_usbhostinitialize(void)
       return pid < 0 ? -ENOEXEC : OK;
     }
 
+  UNUSED(ret);
   return -ENODEV;
 }
 #else

drivers/usbdev/cdcecm.c

@@ -1065,10 +1065,6 @@ static void cdcecm_ipv6multicast(FAR struct cdcecm_driver_s *priv)
 static int cdcecm_ioctl(FAR struct net_driver_s *dev, int cmd,
                       unsigned long arg)
 {
-  FAR struct cdcecm_driver_s *priv =
-    (FAR struct cdcecm_driver_s *)dev->d_private;
-  int ret;
-
   /* Decode and dispatch the driver-specific IOCTL command */
 
   switch (cmd)

fs/partition/fs_ptable.c

@@ -37,6 +37,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <string.h>
+
 #include <nuttx/kmalloc.h>
 
 #include "partition.h"