include/linux/huge_mm.h: return NULL instead of false for pmd_trans_huge_lock()

The return value of pmd_trans_huge_lock() is a pointer, not a boolean
value, so use NULL instead of false as the return value.
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/huge_mm.h

@@ -127,7 +127,7 @@ static inline spinlock_t *pmd_trans_huge_lock(pmd_t *pmd,
 	if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))
 		return __pmd_trans_huge_lock(pmd, vma);
 	else
-		return false;
+		return NULL;
 }
 static inline int hpage_nr_pages(struct page *page)
 {