Move packet scratch declaration to header

src/gps/GPS.h

@@ -106,6 +106,9 @@ class GPS : private concurrency::OSThread
     // Create a ublox packet for editing in memory
     uint8_t makeUBXPacket(uint8_t class_id, uint8_t msg_id, uint8_t payload_size, const uint8_t *msg);
 
+    // scratch space for creating ublox packets
+    uint8_t UBXscratch[250] = {0};
+
   protected:
     /// Do gps chipset specific init, return true for success
     virtual bool setupGPS();
@@ -146,9 +149,6 @@ class GPS : private concurrency::OSThread
 
     void setNumSatellites(uint8_t n);
 
-    // scratch space for creating ublox packets
-    uint8_t UBXscratch[250];
-
   private:
     /// Prepare the GPS for the cpu entering deep or light sleep, expect to be gone for at least 100s of msecs
     /// always returns 0 to indicate okay to sleep