x86/mm/mem_encrypt: Fix erroneous sizeof()

Using sizeof(pointer) for determining the size of a memset() only works
when the size of the pointer and the size of type to which it points are
the same. For pte_t this is only true for 64bit and 32bit-NONPAE. On 32bit
PAE systems this is wrong as the pointer size is 4 byte but the PTE entry
is 8 bytes. It's actually not a real world issue as this code depends on
64bit, but it's wrong nevertheless.

Use sizeof(*p) for correctness sake.

Fixes: aad98391 ("x86/mm/encrypt: Simplify sme_populate_pgd() and sme_populate_pgd_large()")
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: dave.hansen@linux.intel.com
Cc: peterz@infradead.org
Cc: luto@kernel.org
Link: https://lkml.kernel.org/r/1546065252-97996-1-git-send-email-peng.hao2@zte.com.cn

arch/x86/mm/mem_encrypt_identity.c

@@ -158,8 +158,8 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
 	pmd = pmd_offset(pud, ppd->vaddr);
 	if (pmd_none(*pmd)) {
 		pte = ppd->pgtable_area;
-		memset(pte, 0, sizeof(pte) * PTRS_PER_PTE);
-		ppd->pgtable_area += sizeof(pte) * PTRS_PER_PTE;
+		memset(pte, 0, sizeof(*pte) * PTRS_PER_PTE);
+		ppd->pgtable_area += sizeof(*pte) * PTRS_PER_PTE;
 		set_pmd(pmd, __pmd(PMD_FLAGS | __pa(pte)));
 	}