iec61937: incoherent endianness in payload

Order header based on specified endianness and not system endianness
Fix following bugzilla
https://bugzilla.gnome.org/show_bug.cgi?id=678021
https://bugzilla.gnome.org/show_bug.cgi?id=757258

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
1 file changed