watchdog: tegra: enable compile warning as error

watchdog: tegra: enable compile warning as error

- Add compilation flag to treat warning as error
- Handle error of unused variable
- Handle error of uninitialised variable

bug 949219

Change-Id: I07437be5eaa7bf7abe5494c828690b6be3b98178
Signed-off-by: schowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/118039
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sachin Nikam <snikam@nvidia.com>
Rebase-Id: R5158d12bf942a5189cb5a7cbc838096dda4d4915