dax: Fix condition for filling of PMD holes

Currently dax_pmd_fault() decides to fill a PMD-sized hole only if
returned buffer has BH_Uptodate set. However that doesn't get set for
any mapping buffer so that branch is actually a dead code. The
BH_Uptodate check doesn't make any sense so just remove it.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NRoss Zwisler <ross.zwisler@linux.intel.com>

fs/dax.c

@@ -788,7 +788,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
 	i_mmap_lock_read(mapping);
 
-	if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
+	if (!write && !buffer_mapped(&bh)) {
 		spinlock_t *ptl;
 		pmd_t entry;
 		struct page *zero_page = get_huge_zero_page();