MINOR: threads: add a thread-local thread_info pointer "ti"

Since we're likely to access this thread_info struct more frequently in
the future, let's reserve the thread-local symbol to access it directly
and avoid always having to combine thread_info and tid. This pointer is
set when tid is set.
diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 6c420dd..b3c4564 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -56,6 +56,8 @@
 	char __end[0] __attribute__((aligned(64)));
 } thread_info[MAX_THREADS];
 
+extern THREAD_LOCAL struct thread_info *ti; /* thread_info for the current thread */
+
 #define __decl_hathreads(decl)
 #define __decl_spinlock(lock)
 #define __decl_aligned_spinlock(lock)
@@ -140,6 +142,7 @@
 
 static inline void ha_set_tid(unsigned int tid)
 {
+	ti = &thread_info[tid];
 }
 
 static inline void ha_thread_relax(void)
@@ -386,6 +389,7 @@
 
 extern THREAD_LOCAL unsigned int tid;     /* The thread id */
 extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */
+extern THREAD_LOCAL struct thread_info *ti; /* thread_info for the current thread */
 extern volatile unsigned long all_threads_mask;
 extern volatile unsigned long threads_want_rdv_mask;
 extern volatile unsigned long threads_harmless_mask;
@@ -416,6 +420,7 @@
 {
 	tid     = data;
 	tid_bit = (1UL << tid);
+	ti      = &thread_info[tid];
 }
 
 static inline void ha_thread_relax(void)