HAL_PX4: allow for missing SPIDevice table entries

removed panic

libraries/AP_HAL_PX4/SPIDevice.cpp

@@ -176,7 +176,8 @@ SPIDeviceManager::get_device(const char *name)
         }
     }
     if (device_table[i].name == nullptr) {
-        AP_HAL::panic("SPI: invalid device name: %s", name);
+        printf("SPI: Invalid device name: %s\n", name);
+        return AP_HAL::OwnPtr<AP_HAL::SPIDevice>(nullptr);
     }
 
     SPIDesc &desc = device_table[i];