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* Text is no longer updated until a complete group has been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/tuner.c

@@ -24,6 +24,9 @@
 #include "kernel.h"
 #include "tuner.h"
 #include "fmradio.h"
+#ifdef HAVE_RDS_CAP
+#include "rds.h"
+#endif /* HAVE_RDS_CAP */
 
 /* General region information */
 const struct fm_region_data fm_region_data[TUNER_NUM_REGIONS] =
@@ -102,4 +105,24 @@ void tuner_init(void)
     #endif
     }
 }
+
+#ifdef HAVE_RDS_CAP
+size_t tuner_get_rds_info(int setting, void *dst, size_t dstsize)
+{
+    /* TODO: integrate this into tuner_get/set */
+    static const unsigned char info_id_tbl[] =
+    {
+        [RADIO_RDS_NAME]         = RDS_INFO_PS,
+        [RADIO_RDS_TEXT]         = RDS_INFO_RT,
+        [RADIO_RDS_PROGRAM_INFO] = RDS_INFO_PI,
+        [RADIO_RDS_CURRENT_TIME] = RDS_INFO_CT,
+    };
+
+    if ((unsigned int)setting >= ARRAYLEN(info_id_tbl))
+        return 0;
+
+    return rds_pull_info(info_id_tbl[setting], (uintptr_t)dst, dstsize);
+}
+#endif /* HAVE_RDS_CAP */
+
 #endif /* SIMULATOR */