FM: OOB Write & Read Fix

Out of Buffer Write and Read fixes for FM

Change-Id: I9b8e6158d51ca14fb24dfd002ccf0e15a0247df7
diff --git a/helium/radio-helium.h b/helium/radio-helium.h
index d3dae68..4de9213 100644
--- a/helium/radio-helium.h
+++ b/helium/radio-helium.h
@@ -619,7 +619,7 @@
 struct hci_ev_af_list {
     int   tune_freq;
     short   pi_code;
-    char    af_size;
+    uint8_t af_size;
     char    af_list[FM_AF_LIST_MAX_SIZE];
 } __attribute__((packed)) ;
 
@@ -693,7 +693,7 @@
 } __attribute__((packed));
 
 struct hci_fm_data_rd_rsp {
-    char    data_len;
+    uint8_t data_len;
     char    data[DEFAULT_DATA_SIZE];
 } ;
 
@@ -755,6 +755,8 @@
 #define AF_SIZE_OFFSET 6
 #define AF_LIST_OFFSET 7
 #define RT_A_B_FLAG_OFFSET 4
+#define RDS_PS_NUMBER_MIN 1
+#define RDS_PS_NUMBER_MAX 12
 /*FM states*/
 
 enum radio_state_t {