trx/radio_if.py: introduce a new @property 'ready'

Change-Id: I513da0f45c6a608d15fbd0e8eafe14d6af8833d7
diff --git a/python/trx/radio_if.py b/python/trx/radio_if.py
index 93080c4..e15add2 100644
--- a/python/trx/radio_if.py
+++ b/python/trx/radio_if.py
@@ -259,6 +259,16 @@
 		self.stop()
 		self.wait()
 
+	@property
+	def ready(self):
+		# RX / TX frequencies shall be set
+		if self.rx_freq is None:
+			return False
+		if self.tx_freq is None:
+			return False
+
+		return True
+
 	def calc_phase_inc(self, fc):
 		return self.ppm / 1.0e6 * 2 * pi * fc / self.sample_rate