mm/khugepaged: add missed tracepoint for collapse_huge_page_swapin

One return case of `__collapse_huge_page_swapin()` does not invoke
tracepoint while every other return case does. This commit adds a
tracepoint invocation for the case.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: SeongJae Park <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/khugepaged.c

···
 				return false;
 			}
 			/* check if the pmd is still valid */
-			if (mm_find_pmd(mm, address) != pmd)
+			if (mm_find_pmd(mm, address) != pmd) {
+				trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
 				return false;
+			}
 		}
 		if (ret & VM_FAULT_ERROR) {
 			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);