MDEV-14304 Unnecessary conditions in buf_page_get_gen()

Ever since MDEV-10813 cleaned up InnoDB use of atomic memory operations
and made buf_block_fix() an atomic operation, some conditions around
buf_block_fix() have been unnecessary.

storage/innobase/buf/buf0buf.cc

@@ -4263,24 +4263,7 @@ buf_page_get_gen(
 				sure that no state change takes place. */
 				fix_block = block;
 
-				if (fsp_is_system_temporary(page_id.space())) {
-					/* For temporary tablespace,
-					the mutex is being used for
-					synchronization between user
-					thread and flush thread,
-					instead of block->lock. See
-					buf_flush_page() for the flush
-					thread counterpart. */
-
-					BPageMutex*	fix_mutex
-						= buf_page_get_mutex(
-							&fix_block->page);
-					mutex_enter(fix_mutex);
-					buf_block_fix(fix_block);
-					mutex_exit(fix_mutex);
-				} else {
-					buf_block_fix(fix_block);
-				}
+				buf_block_fix(fix_block);
 
 				/* Now safe to release page_hash mutex */
 				rw_lock_x_unlock(hash_lock);
@@ -4371,19 +4354,7 @@ buf_page_get_gen(
 		fix_block = block;
 	}
 
-	if (fsp_is_system_temporary(page_id.space())) {
-		/* For temporary tablespace, the mutex is being used
-		for synchronization between user thread and flush
-		thread, instead of block->lock. See buf_flush_page()
-		for the flush thread counterpart. */
-		BPageMutex*	fix_mutex = buf_page_get_mutex(
-			&fix_block->page);
-		mutex_enter(fix_mutex);
-		buf_block_fix(fix_block);
-		mutex_exit(fix_mutex);
-	} else {
-		buf_block_fix(fix_block);
-	}
+	buf_block_fix(fix_block);
 
 	/* Now safe to release page_hash mutex */
 	rw_lock_s_unlock(hash_lock);