stellaris: recover_command use usleep rather than sleep

windows api does not define a posix sleep, use usleep that
has an openocd wrapper to the win32 native function.
Signed-off-by: Spencer Oliver <ntfreak@users.sourceforge.net>

src/flash/nor/stellaris.c

@@ -1215,7 +1215,7 @@ COMMAND_HANDLER(stellaris_handle_recover_command)
 	retval = jtag_execute_queue();
 
 	/* wait 400+ msec ... OK, "1+ second" is simpler */
-	sleep(1);
+	usleep(1000);
 
 	/* USER INTERVENTION required for the power cycle
 	 * Restarting OpenOCD is likely needed because of mode switching.