AP_Generator: fixed misaligned access in RicenPower

libraries/AP_Generator/AP_Generator_RichenPower.cpp

@@ -112,8 +112,9 @@ bool AP_Generator_RichenPower::get_reading()
 
     // calculate checksum....
     uint16_t checksum = 0;
+    const uint8_t *checksum_buffer = &u.parse_buffer[2];
     for (uint8_t i=0; i<5; i++) {
-        checksum += be16toh(checksum_buffer[i]);
+        checksum += be16toh_ptr(&checksum_buffer[2*i]);
     }
 
     if (checksum != be16toh(u.packet.checksum)) {

libraries/AP_Generator/AP_Generator_RichenPower.h

@@ -156,7 +156,6 @@ private:
         struct RichenPacket packet;
     };
     RichenUnion u;
-    uint16_t *checksum_buffer = (uint16_t*)&u.parse_buffer[2];
 
     uint8_t body_length;