erofs: fix to add missing tracepoint in erofs_readahead()

Commit 771c994 ("erofs: convert all uncompressed cases to iomap")
converts to use iomap interface, it removed trace_erofs_readahead()
tracepoint in the meantime, let's add it back.

Fixes: 771c994 ("erofs: convert all uncompressed cases to iomap")
Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250707084832.2725677-1-chao@kernel.org
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: chaseyu

fs/erofs/data.c

@@ -356,6 +356,9 @@ static int erofs_read_folio(struct file *file, struct folio *folio)
 
 static void erofs_readahead(struct readahead_control *rac)
 {
+	trace_erofs_readahead(rac->mapping->host, readahead_index(rac),
+					readahead_count(rac), true);
+
 	return iomap_readahead(rac, &erofs_iomap_ops);
 }