SDR: Add option to set local oscillator (LO) offset

By default it is set to -1 MHz.

src/libmobile/main_mobile.c

@@ -43,6 +43,8 @@
 #include "../libsdr/sdr_config.h"
 #endif
 
+#define DEFAULT_LO_OFFSET -1000000.0
+
 static int got_init = 0;
 
 /* common mobile settings */
@@ -77,7 +79,7 @@ void main_mobile_init(void)
 {
 	got_init = 1;
 #ifdef HAVE_SDR
-	sdr_config_init();
+	sdr_config_init(DEFAULT_LO_OFFSET);
 #endif
 }