genicam: try to compute correctly lsb and msb from big endian architecture.
genicam: try to compute correctly lsb and msb from big endian architecture.

Add an assertion in the hots big endian case. It's not tested and will
be probably wrongly implemented.

lu-zero/aravis,AnilRamachandran/aravis,AravisProject/aravis,AravisProject/aravis,AravisProject/aravis,lu-zero/aravis,AnilRamachandran/aravis,AravisProject/aravis,AravisProject/aravis,AnilRamachandran/aravis,lu-zero/aravis,AnilRamachandran/aravis,lu-zero/aravis,AnilRamachandran/aravis,lu-zero/aravis