mm: fix various kernel-doc comments

Fix various kernel-doc notation in mm/:

filemap.c: add function short description; convert 2 to kernel-doc
fremap.c: change parameter 'prot' to @prot
pagewalk.c: change "-" in function parameters to ":"
slab.c: fix short description of kmem_ptr_validate()
swap.c: fix description & parameters of put_pages_list()
swap_state.c: fix function parameters
vmalloc.c: change "@returns" to "Returns:" since that is not a parameter

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ec42f01..50757ee 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -115,6 +115,7 @@
 /**
  * add_to_swap - allocate swap space for a page
  * @page: page we want to move to swap
+ * @gfp_mask: memory allocation flags
  *
  * Allocate swap space for the page and add the page to the
  * swap cache.  Caller needs to hold the page lock. 
@@ -315,6 +316,7 @@
 /**
  * swapin_readahead - swap in pages in hope we need them soon
  * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
  * @vma: user vma this address belongs to
  * @addr: target address for mempolicy
  *