Change choffset to use channel RF A in B210

targets/ARCH/USRP/USERSPACE/LIB/usrp_lib.cpp

@@ -940,7 +940,7 @@ extern "C" {
     LOG_I(HW, "openair0_cfg[0].sdr_addrs == '%s'\n", openair0_cfg[0].sdr_addrs);
     LOG_I(HW, "openair0_cfg[0].clock_source == '%d' (internal = %d, external = %d)\n", openair0_cfg[0].clock_source,internal,external);
     usrp_state_t *s ;
-    int choffset = 1;
+    int choffset = 0;
 
     if ( device->priv == NULL) {
       s=(usrp_state_t *)calloc(sizeof(usrp_state_t),1);