s390/mm: simplify get_guest_storage_key

We can safe a few LOC and make that function easier to understand
by rewriting existing code.
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/mm/pgtable.c

@@ -551,20 +551,11 @@ unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
 		return -EFAULT;
 
 	pgste = pgste_get_lock(ptep);
-	if (pte_val(*ptep) & _PAGE_INVALID) {
-		key  = (pgste_val(pgste) & PGSTE_ACC_BITS) >> 56;
-		key |= (pgste_val(pgste) & PGSTE_FP_BIT) >> 56;
-		key |= (pgste_val(pgste) & PGSTE_GR_BIT) >> 48;
-		key |= (pgste_val(pgste) & PGSTE_GC_BIT) >> 48;
-	} else {
+	key = (pgste_val(pgste) & (PGSTE_ACC_BITS | PGSTE_FP_BIT)) >> 56;
+	if (!(pte_val(*ptep) & _PAGE_INVALID))
 		key = page_get_storage_key(pte_val(*ptep) & PAGE_MASK);
-
 	/* Reflect guest's logical view, not physical */
-		if (pgste_val(pgste) & PGSTE_GR_BIT)
-			key |= _PAGE_REFERENCED;
-		if (pgste_val(pgste) & PGSTE_GC_BIT)
-			key |= _PAGE_CHANGED;
-	}
+	key |= (pgste_val(pgste) & (PGSTE_GR_BIT | PGSTE_GC_BIT)) >> 48;
 	pgste_set_unlock(ptep, pgste);
 	pte_unmap_unlock(ptep, ptl);
 	return key;