V4L/DVB (8126): net endianness fix

According to RFC 4326 (4.1) D-bit is MSB in net-endian 16bit.
dvb_net.c did
				/* Set D-bit for CRC32 verification,
				 * if it was set originally. */
				ulen |= 0x0080;
which works of little-endian (htons(1<<15) is 0x0080 there), but breaks
on big-endian.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>