arm64: mm: Fix column alignment for UXN in kernel_page_tables

UXN is the only individual PTE bit other than the PTE_ATTRINDX_MASK ones
which doesn't have both a set and a clear value provided, meaning that the
columns in the table won't all be aligned. The PTE_ATTRINDX_MASK values
are all both mutually exclusive and longer so are listed last to make a
single final column for those values. Ensure everything is aligned by
providing a clear value for UXN.
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/dump.c

@@ -142,6 +142,7 @@ static const struct prot_bits pte_bits[] = {
 		.mask	= PTE_UXN,
 		.val	= PTE_UXN,
 		.set	= "UXN",
+		.clear	= "   ",
 	}, {
 		.mask	= PTE_ATTRINDX_MASK,
 		.val	= PTE_ATTRINDX(MT_DEVICE_nGnRnE),