cp/cmp: Add WATCHDOG_RESET in copy and compare loop

On some boards with a very short watchdog timeout, the "cp" and
"cmp" commands may reset the board. This patch adds some
watchdog resets inside the loops. Otherwise for example the lwmon5
board will reset while doing something like this:

=> cp.b fc000000 1000000 100000
Signed-off-by: NStefan Roese <sr@denx.de>

common/cmd_mem.c

@@ -337,6 +337,10 @@ int do_mem_cmp (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 		ngood++;
 		addr1 += size;
 		addr2 += size;
+
+		/* reset watchdog from time to time */
+		if ((count % (64 << 10)) == 0)
+			WATCHDOG_RESET();
 	}
 
 	printf("Total of %ld %s%s were the same\n",
@@ -447,6 +451,10 @@ int do_mem_cp ( cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 			*((u_char *)dest) = *((u_char *)addr);
 		addr += size;
 		dest += size;
+
+		/* reset watchdog from time to time */
+		if ((count % (64 << 10)) == 0)
+			WATCHDOG_RESET();
 	}
 	return 0;
 }