mpm: x4xx: Add log message for older DIO boards

Older DIO boards don't support all the features of newer ones, but from
the log messages, it's not clear what revision the board has. We add
a log statement to clarify.

mpm/python/usrp_mpm/periph_manager/x4xx_dio_control.py

@@ -229,7 +229,8 @@ class DioControl:
         self.port_control = {port: self._PortControl(port) for port in self.DIO_PORTS}
         self.mboard_regs = mboard_regs
         self.mboard_cpld = mboard_cpld
-
+        if self.mboard_regs.get_compat_number() < self.FULL_DIO_FPGA_COMPAT:
+            self.log.warning("DIO board does not support the full feature set.")
         # initialize port mapping for HDMI and DIO
         self.port_mappings = {}
         self.mapping = None