ww-mutex: Fix the ww_acquire_ctx function annotations

ww-mutex: Fix the ww_acquire_ctx function annotations

The ww_acquire_done() call is optional. Reflect this in the annotations of
ww_acquire_done().

Fixes: 47907461e4f6 ("locking/ww_mutex: Support Clang's context analysis")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Marco Elver <elver@google.com>
Link: https://patch.msgid.link/20260225183244.4035378-4-bvanassche@acm.org