tests: Add simple CAN test.

tests/pyb/can.py

@@ -0,0 +1,9 @@
+from pyb import CAN
+
+can = CAN(1)
+print(can)
+can.init(CAN.LOOPBACK)
+print(can.any(0))
+can.send('abcd', 123)
+print(can.any(0))
+print(can.recv(0))

tests/pyb/can.py.exp

@@ -0,0 +1,4 @@
+CAN(1)
+False
+True
+(123, 0, 0, b'abcd')