mm/page_exit: fix kernel doc warning in page_ext_put()

Fix the below compiler warnings reported with 'make W=1 mm/'. 
mm/page_ext.c:178: warning: Function parameter or member 'page_ext' not
described in 'page_ext_put'.

[quic_pkondeti@quicinc.com: better patch title]
Link: https://lkml.kernel.org/r/1667884582-2465-1-git-send-email-quic_charante@quicinc.com
Fixes: b1d5488a ("mm: fix use-after free of page_ext after race with memory-offline")
Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavan Kondeti <quic_pkondeti@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_ext.c

@@ -166,7 +166,7 @@ struct page_ext *page_ext_get(struct page *page)
 
 /**
  * page_ext_put() - Working with page extended information is done.
- * @page_ext - Page extended information received from page_ext_get().
+ * @page_ext: Page extended information received from page_ext_get().
  *
  * The page extended information of the page may not be valid after this
  * function is called.