seqlock: add missing parameter documentation for raw_seqcount_try_begin()

Add missing documentation for raw_seqcount_try_begin() start parameter.

Link: https://lkml.kernel.org/r/20250116182730.801497-1-surenb@google.com
Fixes: dba4761 ("seqlock: add raw_seqcount_try_begin")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/all/20250116170522.23e884d5@canb.auug.org.au/
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: surenbaghdasaryan

include/linux/seqlock.h

@@ -322,6 +322,7 @@ SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
  * raw_seqcount_try_begin() - begin a seqcount_t read critical section
  *                            w/o lockdep and w/o counter stabilization
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ * @start: count to be passed to read_seqcount_retry()
  *
  * Similar to raw_seqcount_begin(), except it enables eliding the critical
  * section entirely if odd, instead of doing the speculation knowing it will