mm/truncate.c: make __invalidate_mapping_pages() static

Fix the following sparse warning:

mm/truncate.c:531:15: warning: symbol '__invalidate_mapping_pages' was not declared. Should it be static?

Fixes: eb1d7a65f08a ("mm, fadvise: improve the expensive remote LRU cache draining after FADV_DONTNEED")
Signed-off-by: Jason Yan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Reviewed-by: Yafang Shao <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

mm/truncate.c

···
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);
 
-unsigned long __invalidate_mapping_pages(struct address_space *mapping,
+static unsigned long __invalidate_mapping_pages(struct address_space *mapping,
 		pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
 {
 	pgoff_t indices[PAGEVEC_SIZE];