Fix test of range of skip= argument in NSH dd command. From Ken Petit

ChangeLog.txt

@@ -529,3 +529,6 @@
 	* apps/examples/ostest:  In the non-cancelable thread test, we need
 	  to give the thread an opportunity to run and to set the non-
 	  cancelable state.
+	* apps/nshlib/nsh_ddcmd.c: Correct the test of the skip input
+	  parameter.  Was limiting the range to <= count.  From Ken
+	  Petit (2014-4-24).

nshlib/nsh_ddcmd.c

@@ -545,12 +545,6 @@ int cmd_dd(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
     }
 #endif
 
-  if (dd.skip > dd.nsectors)
-    {
-      nsh_output(vtbl, g_fmtarginvalid, g_dd);
-      goto errout_with_paths;
-    }
-
   /* Allocate the I/O buffer */
 
   dd.buffer = malloc(dd.sectsize);