stmhal/can: Fix a bug in filter handling.

Reported here: http://forum.micropython.org/viewtopic.php?f=2&t=845

tests/pyb/can.py

@@ -58,6 +58,26 @@ else:
     else:
         print('failed, wrong data received')
 
+# Test filters
+for n in [0, 8, 16, 24]:
+    filter_id = 0b00001000 << n
+    filter_mask = 0b00011100 << n
+    id_ok = 0b00001010 << n
+    id_fail = 0b00011010 << n
+
+    can.clearfilter(0)
+    can.setfilter(0, pyb.CAN.MASK32, 0, (filter_id, filter_mask))
+
+    can.send('ok', id_ok, timeout=3)
+    if can.any(0):
+        msg = can.recv(0)
+        print((hex(filter_id), hex(filter_mask), hex(msg[0]), msg[3]))
+
+    can.send("fail", id_fail, timeout=3)
+    if can.any(0):
+        msg = can.recv(0)
+        print((hex(filter_id), hex(filter_mask), hex(msg[0]), msg[3]))
+
 del can
 
 # Test RxCallbacks

tests/pyb/can.py.exp

@@ -16,6 +16,10 @@ True
 passed
 CAN(1, CAN.LOOPBACK, extframe=True)
 passed
+('0x8', '0x1c', '0xa', b'ok')
+('0x800', '0x1c00', '0xa00', b'ok')
+('0x80000', '0x1c0000', '0xa0000', b'ok')
+('0x8000000', '0x1c000000', '0xa000000', b'ok')
 cb0
 pending
 cb0