Fix #4911 : Partially rework some code to remove warnings about potential non-aligned memory accesses (#4912)

* * Adding the -Wcast-align compilation flag for
  the rp2040.

* * Some rework to use a struct to access radio data
* Buffer will not be accessed by arithmetic pointer anymore

* * Remplace arithmetic pointer to avoid Warning

* * Avoid 2 little artitmetic pointer

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/gps/GPS.cpp

@@ -91,9 +91,9 @@ void GPS::CASChecksum(uint8_t *message, size_t length)
 
     // Iterate over the payload as a series of uint32_t's and
     // accumulate the cksum
-    uint32_t const *payload = (uint32_t *)(message + 6);
     for (size_t i = 0; i < (length - 10) / 4; i++) {
-        uint32_t pl = payload[i];
+        uint32_t pl = 0;
+        memcpy(&pl, (message + 6) + (i * sizeof(uint32_t)), sizeof(uint32_t)); // avoid pointer dereference
         cksum += pl;
     }