AP_GSOF: Use memcpy for structs

[Ryanf55]

... having looked at this, we're making the situation worse in here in terms of mixing up on-the-wire structures and in-memory structures, and my suggestions above would make the code rather better (i.e. just memcpy and convert on the way out of the structure).

However, I can't insist on that in this PR - you're good to leave this as-is

Originally posted by @peterbarker in #30232 (comment)

[peterbarker]

Note that my memcpy suggest would leave the structures as PACKED.