Improve radio RDS driver and framework

* Remove unused bits like the radio event and simplify basic
radio interface. It can be more self-contained with rds.h only
required by radio and tuner code.

* Add post-processing to text a-la Silicon Labs AN243. The chip's
error correction can only do so much; additional checks are highly
recommended. Simply testing for two identical messages in a row
is extremely effective and I've never seen corrupted text since
doing that, even with mediocre reception.

Groups segments must arrive in order, not randomly; logic change
only accepts them in order, starting at 0.

Time readout was made a bit better but really we'd need to use
verbose mode and ensure that no errors were seen during receiving
of time and more checks would be need to have a stable PI. The
text is the important bit anyway.

* Time out of stale text.

* Text is no longer updated until a complete group has been
received, as is specified in the standard. Perhaps go back to
scrolling text lines in the radio screen?

* Add proper character conversion to UTF-8. Only the default G0
table for the moment. The other two could be added in.

* Add variants "RDS_CFG_PROCESS" and "RDS_CFG_PUSH" to allow
the option for processed RDS data to be pushed to the driver and
still do proper post-processing (only text conversion for now for
the latter).

Change-Id: I4d83f8b2e89a209a5096d15ec266477318c66925

firmware/export/config.h

@@ -712,6 +712,16 @@ Lyre prototype 1 */
 #define BATTERY_CAPACITY_INC 0
 #endif
 
+#ifdef HAVE_RDS_CAP
+/* combinable bitflags */
+#define RDS_CFG_ISR     0x1 /* uses ISR to process packets */
+#define RDS_CFG_PROCESS 0x2 /* uses raw packet processing */
+#define RDS_CFG_PUSH    0x4 /* pushes processed information */
+#ifndef CONFIG_RDS
+#define CONFIG_RDS  RDS_CFG_PROCESS /* thread processing+raw processing */
+#endif /* CONFIG_RDS */
+#endif /* HAVE_RDS_CAP */
+
 #ifndef CONFIG_ORIENTATION
 #if LCD_HEIGHT > LCD_WIDTH
 #define CONFIG_ORIENTATION SCREEN_PORTRAIT