tegra: camera race condition vulnerability

tegra: camera race condition vulnerability

- Add mutex_lock(cam_desc.d_mutex) around ioctl access functions.
- Check cam->cdev in PCLLK_IOCTL_DEV_DEL ioctl.

(Back ported from Nexus N9 project)

Bug 1832830

Signed-off-by: <tiangangpi@gmail.com>
Signed-off-by: Xiaya Hu <xiaya@nvidia.com>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 28026625
Change-Id: I81fbab628fb6516afa2cf5d3e0adf333aa2eb003
Reviewed-on: http://git-master/r/1271370
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Frank Chen <frankc@nvidia.com>
Tested-by: Frank Chen <frankc@nvidia.com>
Reviewed-by: Jihoon Bang <jbang@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>