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/vmalloc.c b/mm/vmalloc.c
index 950c0be..ecf91f8 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -757,7 +757,8 @@
  *	@vma:		vma to cover (map full range of vma)
  *	@addr:		vmalloc memory
  *	@pgoff:		number of pages into addr before first page to map
- *	@returns:	0 for success, -Exxx on failure
+ *
+ *	Returns:	0 for success, -Exxx on failure
  *
  *	This function checks that addr is a valid vmalloc'ed area, and
  *	that it is big enough to cover the vma. Will return failure if
@@ -829,7 +830,8 @@
 /**
  *	alloc_vm_area - allocate a range of kernel address space
  *	@size:		size of the area
- *	@returns:	NULL on failure, vm_struct on success
+ *
+ *	Returns:	NULL on failure, vm_struct on success
  *
  *	This function reserves a range of kernel address space, and
  *	allocates pagetables to map that range.  No actual mappings