[media] drx-j: get rid of its own be??_to_cpu() implementation

Instead of handling endiannes with its own internal way, use the
already existing macros.

Acked-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>