f2fs: fix to avoid overflow while left shift operation

Should cast type of folio->index from pgoff_t to loff_t to avoid overflow
while left shift operation.

Fixes: 3265d3d ("f2fs: support partial truncation on compressed inode")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: chaseyu

fs/f2fs/compress.c

@@ -1245,7 +1245,7 @@ int f2fs_truncate_partial_cluster(struct inode *inode, u64 from, bool lock)
 
 		for (i = cluster_size - 1; i >= 0; i--) {
 			struct folio *folio = page_folio(rpages[i]);
-			loff_t start = folio->index << PAGE_SHIFT;
+			loff_t start = (loff_t)folio->index << PAGE_SHIFT;
 
 			if (from <= start) {
 				folio_zero_segment(folio, 0, folio_size(folio));