s390/mm: Fix DirectMap accounting

With uncoupling of physical and virtual address spaces population of
the identity mapping was changed to use the type POPULATE_IDENTITY
instead of POPULATE_DIRECT. This breaks DirectMap accounting:

> cat /proc/meminfo
DirectMap4k:       55296 kB
DirectMap1M:    18446744073709496320 kB

Adjust all locations of update_page_count() in vmem.c to use
POPULATE_IDENTITY instead of POPULATE_DIRECT as well. With this
accounting is correct again:

> cat /proc/meminfo
DirectMap4k:       54264 kB
DirectMap1M:     8334336 kB

Fixes: c98d2ec ("s390/mm: Uncouple physical vs virtual address spaces")
Cc: stable@vger.kernel.org
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: hcahca

arch/s390/boot/vmem.c

@@ -306,7 +306,7 @@ static void pgtable_pte_populate(pmd_t *pmd, unsigned long addr, unsigned long e
 			pages++;
 		}
 	}
-	if (mode == POPULATE_DIRECT)
+	if (mode == POPULATE_IDENTITY)
 		update_page_count(PG_DIRECT_MAP_4K, pages);
 }
 
@@ -339,7 +339,7 @@ static void pgtable_pmd_populate(pud_t *pud, unsigned long addr, unsigned long e
 		}
 		pgtable_pte_populate(pmd, addr, next, mode);
 	}
-	if (mode == POPULATE_DIRECT)
+	if (mode == POPULATE_IDENTITY)
 		update_page_count(PG_DIRECT_MAP_1M, pages);
 }
 
@@ -372,7 +372,7 @@ static void pgtable_pud_populate(p4d_t *p4d, unsigned long addr, unsigned long e
 		}
 		pgtable_pmd_populate(pud, addr, next, mode);
 	}
-	if (mode == POPULATE_DIRECT)
+	if (mode == POPULATE_IDENTITY)
 		update_page_count(PG_DIRECT_MAP_2G, pages);
 }