mm: pagemap.h: fix two kernel-doc markups

Changeset a8cf7f2 ("mm: add find_lock_head") renamed the
index parameter, but forgot to update the kernel-doc markups
accordingly.

Fixes: a8cf7f2 ("mm: add find_lock_head")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/dce89b296a4f5f9f8f798d5e76b6736c14a916ac.1603791716.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Author: mchehab

include/linux/pagemap.h

@@ -344,9 +344,9 @@ static inline struct page *find_get_page_flags(struct address_space *mapping,
 /**
  * find_lock_page - locate, pin and lock a pagecache page
  * @mapping: the address_space to search
- * @offset: the page index
+ * @index: the page index
  *
- * Looks up the page cache entry at @mapping & @offset.  If there is a
+ * Looks up the page cache entry at @mapping & @index.  If there is a
  * page cache page, it is returned locked and with an increased
  * refcount.
  *
@@ -363,9 +363,9 @@ static inline struct page *find_lock_page(struct address_space *mapping,
 /**
  * find_lock_head - Locate, pin and lock a pagecache page.
  * @mapping: The address_space to search.
- * @offset: The page index.
+ * @index: The page index.
  *
- * Looks up the page cache entry at @mapping & @offset.  If there is a
+ * Looks up the page cache entry at @mapping & @index.  If there is a
  * page cache page, its head page is returned locked and with an increased
  * refcount.
  *