mm: fix get_mctgt_type() kernel-doc

Convert the return values to an ReST list and tidy up the wording while
I'm touching it.

[akpm@linux-foundation.org: changes suggested by Randy]
[willy@infradead.org: another change suggested by Randy]
  Link: https://lkml.kernel.org/r/ZOUZtZizeQG7PcsM@casper.infradead.org
Link: https://lkml.kernel.org/r/20230818200630.2719595-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Matthew Wilcox (Oracle)

mm/memcontrol.c

@@ -5850,25 +5850,20 @@ static int mem_cgroup_move_account(struct page *page,
  * @ptent: the pte to be checked
  * @target: the pointer the target page or swap ent will be stored(can be NULL)
  *
- * Returns
- *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
- *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
- *     move charge. if @target is not NULL, the page is stored in target->page
- *     with extra refcnt got(Callers should handle it).
- *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
- *     target for charge migration. if @target is not NULL, the entry is stored
- *     in target->ent.
- *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is device memory and
- *   thus not on the lru.
- *     For now we such page is charge like a regular page would be as for all
- *     intent and purposes it is just special memory taking the place of a
- *     regular page.
- *
- *     See Documentations/vm/hmm.txt and include/linux/hmm.h
- *
- * Called with pte lock held.
+ * Context: Called with pte lock held.
+ * Return:
+ * * MC_TARGET_NONE - If the pte is not a target for move charge.
+ * * MC_TARGET_PAGE - If the page corresponding to this pte is a target for
+ *   move charge. If @target is not NULL, the page is stored in target->page
+ *   with extra refcnt taken (Caller should release it).
+ * * MC_TARGET_SWAP - If the swap entry corresponding to this pte is a
+ *   target for charge migration.  If @target is not NULL, the entry is
+ *   stored in target->ent.
+ * * MC_TARGET_DEVICE - Like MC_TARGET_PAGE but page is device memory and
+ *   thus not on the lru.  For now such page is charged like a regular page
+ *   would be as it is just special memory taking the place of a regular page.
+ *   See Documentations/vm/hmm.txt and include/linux/hmm.h
  */
-
 static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		unsigned long addr, pte_t ptent, union mc_target *target)
 {