fm: Return frequency value in getFrequency

Return frequency value in getFrequency if call to function is successful
instead of error value.

Change-Id: I07d62aecbfc396ec94f4b1efb8fd096499a7e3bb
diff --git a/helium/radio-helium.h b/helium/radio-helium.h
index a67c981..070dafa 100644
--- a/helium/radio-helium.h
+++ b/helium/radio-helium.h
@@ -1241,7 +1241,7 @@
 struct fm_interface_t {
     int (*init)(const fm_hal_callbacks_t *p_cb);
     int (*set_fm_ctrl)(int opcode, int val);
-    void (*Get_fm_ctrl) (int opcode, int val);
+    void (*get_fm_ctrl) (int opcode, int *val);
 };
 
 #endif /* __UAPI_RADIO_HCI_CORE_H */