powerpc/book3e: Fix PUD allocation size in map_kernel_page()

Commit 2fb4706 ("powerpc: add support for folded p4d page tables")
erroneously changed PUD setup to a mix of PMD and PUD. Fix it.

While at it, use PTE_TABLE_SIZE instead of PAGE_SIZE for PTE tables
in order to avoid any confusion.

Fixes: 2fb4706 ("powerpc: add support for folded p4d page tables")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/95ddfd6176d53e6c85e13bd1c358359daa56775f.1655974558.git.christophe.leroy@csgroup.eu

Author: chleroy

arch/powerpc/mm/nohash/book3e_pgtable.c

@@ -96,8 +96,8 @@ int __ref map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
 		pgdp = pgd_offset_k(ea);
 		p4dp = p4d_offset(pgdp, ea);
 		if (p4d_none(*p4dp)) {
-			pmdp = early_alloc_pgtable(PMD_TABLE_SIZE);
-			p4d_populate(&init_mm, p4dp, pmdp);
+			pudp = early_alloc_pgtable(PUD_TABLE_SIZE);
+			p4d_populate(&init_mm, p4dp, pudp);
 		}
 		pudp = pud_offset(p4dp, ea);
 		if (pud_none(*pudp)) {
@@ -106,7 +106,7 @@ int __ref map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
 		}
 		pmdp = pmd_offset(pudp, ea);
 		if (!pmd_present(*pmdp)) {
-			ptep = early_alloc_pgtable(PAGE_SIZE);
+			ptep = early_alloc_pgtable(PTE_TABLE_SIZE);
 			pmd_populate_kernel(&init_mm, pmdp, ptep);
 		}
 		ptep = pte_offset_kernel(pmdp, ea);