tomoyo: Use scoped init guard

tomoyo: Use scoped init guard

Convert lock initialization to scoped guarded initialization where
lock-guarded members are initialized in the same scope.

This ensures the context analysis treats the context as active during member
initialization. This is required to avoid errors once implicit context
assertion is removed.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260119094029.1344361-6-elver@google.com