video: tegra: host: fix Coverity issues

video: tegra: host: fix Coverity issues

- fix unchecked return value from sscanf
Coverity id : 25029
- fix explicit NULL dereference of pdata
Coverity id : 25086

Bug 1416640

Change-Id: I56749f9e15d70b9bffaa85435a6d39a301413cab
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/337790
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Shridhar Rasal <srasal@nvidia.com>
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: Sachin Nikam <snikam@nvidia.com>