crypto: Enable context analysis

crypto: Enable context analysis

Enable context analysis for crypto subsystem.

This demonstrates a larger conversion to use Clang's context
analysis. The benefit is additional static checking of locking rules,
along with better documentation.

Note the use of the __acquire_ret macro how to define an API where a
function returns a pointer to an object (struct scomp_scratch) with a
lock held. Additionally, the analysis only resolves aliases where the
analysis unambiguously sees that a variable was not reassigned after
initialization, requiring minor code changes.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-36-elver@google.com