HAL_Linux: fixed build warnings in RC input methods

libraries/AP_HAL_Linux/RCInput_UART.h

@@ -22,7 +22,7 @@ private:
     int _fd;
     uint8_t *_pdata;
     ssize_t _remain;
-    struct PACKED {
+    struct {
         uint16_t magic;
         uint16_t values[CHANNELS];
     } _data;

libraries/AP_HAL_Linux/RCInput_UDP.cpp

@@ -79,5 +79,7 @@ void RCInput_UDP::_timer_tick(void)
     _last_buf_ts = _buf.timestamp_us;
     _last_buf_seq = _buf.sequence;
 
-    _update_periods(_buf.pwms, n_channels);
+    uint16_t pwms[n_channels];
+    memcpy(pwms, _buf.pwms, n_channels*sizeof(uint16_t));
+    _update_periods(pwms, n_channels);
 }