They are implicitly zero-initialized, remove explicit initialization.
It keeps the upcoming additions to kcsan_ctx consistent with the rest.

No functional change intended.
Signed-off-by: NMarco Elver <elver@google.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NPaul E. McKenney <paulmck@kernel.org>