r92su: try to fix high byte vs low byte swap for big endian system

José Vázquez reported a issue with r92su. The usbmon
log he sent me did reveal that the address bytes are
swapped on big endian architectures.

(Big Endian)
Ci: s c0 05 0400 0000 0004 4 <
Ci: s c0 05 0a00 0000 0001 1 <

vs.

(Little Endian)
Ci: s c0 05 0004 0000 0004 4 <
Ci: s c0 05 000a 0000 0001 1 <

Reported-by: José Vázquez <ppvazquezfer@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>