[media] saa7164: fix endian conversion in saa7164_bus_set()

The msg->command field is 32 bits, and we should fill it with a call
to cpu_to_le32().  The current code is broke on big endian systems.
On little endian systems it truncates the 32 bit value to 16 bits
which probably still works fine.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>