x86/boot/64: Apply encryption mask to 5-level pagetable update

When running with 5-level page tables, the kernel mapping PGD entry is
updated to point to the P4D table. The assignment uses _PAGE_TABLE_NOENC,
which, when SME is active (mem_encrypt=on), results in a page table
entry without the encryption mask set, causing the system to crash on
boot.

Change the assignment to use _PAGE_TABLE instead of _PAGE_TABLE_NOENC so
that the encryption mask is set for the PGD entry.

Fixes: 533568e0 ("x86/boot/64: Use RIP_REL_REF() to access early_top_pgt[]")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/8f20345cda7dbba2cf748b286e1bc00816fe649a.1711122067.git.thomas.lendacky@amd.com

arch/x86/kernel/head64.c

@@ -175,7 +175,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
 		p4d = (p4dval_t *)&RIP_REL_REF(level4_kernel_pgt);
 		p4d[MAX_PTRS_PER_P4D - 1] += load_delta;
 
-		pgd[pgd_index(__START_KERNEL_map)] = (pgdval_t)p4d | _PAGE_TABLE_NOENC;
+		pgd[pgd_index(__START_KERNEL_map)] = (pgdval_t)p4d | _PAGE_TABLE;
 	}
 
 	RIP_REL_REF(level3_kernel_pgt)[PTRS_PER_PUD - 2].pud += load_delta;