HAL_ChibiOS: use pullup on CTS line

this makes life less difficult for SiK radios which go into bootloader
mode on low CTS

libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py

@@ -247,11 +247,6 @@ class generic_pin(object):
              self.label.endswith('_RX') or
              self.label.endswith('_CTS') or
              self.label.endswith('_RTS'))):
-            # default RX/TX lines to pullup, to prevent spurious bytes
-            # on disconnected ports. CTS is the exception, which is pulldown
-            if self.label.endswith("CTS"):
-                v = "PULLDOWN"
-            else:
                 v = "PULLUP"
         for e in self.extra:
             if e in values: