cirrus: delete GCC 4.6 warnings

Commit 92d675d1c1f23f3617e24b63c825074a1d1da44b triggered uninitialized
variables warning with GCC 4.6. Fix them by adding zero initializers.

Acked-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
