[media] gspca - ov534/ov534_9: Fix sccd_read/write errors

The ov534 bridge is too slow to handle the sensor accesses
requested by fast hosts giving 'sccb_reg_write failed'.
A small delay fixes the problem.

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>