f2fs: use ra_meta_pages to simplify readahead code in restore_node_summary
f2fs: use ra_meta_pages to simplify readahead code in restore_node_summary

Use more common function ra_meta_pages() with META_POR to readahead node blocks
in restore_node_summary() instead of ra_sum_pages(), hence we can simplify the
readahead code there, and also we can remove unused function ra_sum_pages().

changes from v2:
 o use invalidate_mapping_pages as before suggested by Changman Lee.
changes from v1:
 o fix one bug when using truncate_inode_pages_range which is pointed out by
   Jaegeuk Kim.

Reviewed-by: Changman Lee <f10da886ecf5f6d400f766170992d382feccd416@samsung.com>
Signed-off-by: Chao Yu <0cc5db7488e13b393f245aa6263acec5e92fdcc5@samsung.com>
Signed-off-by: Jaegeuk Kim <71255387a32c360dfbe6dfb7aaeb123bf1dc8cb6@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs