ENGR00119582 V4L2 capture:Fix race condition for accessing kernel resource

Some kernel resource can be accessed in interrupt handler and user
controlled V4L2 ioctrls, so there is a race condition which makes
the kernel malfunction potentially.

Signed-off-by: Liu Ying <b17645@freescale.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>