Rover: move should_log check of log bitmask into DataFlash

APMrover2/Rover.cpp

@@ -24,7 +24,7 @@ Rover::Rover(void) :
     channel_steer(nullptr),
     channel_throttle(nullptr),
     channel_learn(nullptr),
-    DataFlash{FIRMWARE_STRING},
+    DataFlash{FIRMWARE_STRING, g.log_bitmask},
     modes(&g.mode1),
     L1_controller(ahrs, nullptr),
     nav_controller(&L1_controller),

APMrover2/system.cpp

@@ -502,10 +502,7 @@ uint8_t Rover::check_digital_pin(uint8_t pin)
  */
 bool Rover::should_log(uint32_t mask)
 {
-    if (!(mask & g.log_bitmask)) {
-        return false;
-    }
-    if (!DataFlash.should_log()) {
+    if (!DataFlash.should_log(mask)) {
         return false;
     }
     start_logging();