KVM: arm64: nv: Truely enable nXS TLBI operations

Although we now have support for nXS-flavoured TLBI instructions,
we still don't expose the feature to the guest thanks to a mixture
of misleading comment and use of a bunch of magic values.

Fix the comment and correctly express the masking of LS64, which
is enough to expose nXS to the world. Not that anyone cares...
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240703154743.824824-1-maz@kernel.orgSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/kvm/nested.c

@@ -810,8 +810,8 @@ static u64 limit_nv_id_reg(u32 id, u64 val)
 		break;
 
 	case SYS_ID_AA64ISAR1_EL1:
-		/* Support everything but Spec Invalidation */
-		val &= ~(GENMASK_ULL(63, 56)	|
+		/* Support everything but Spec Invalidation and LS64 */
+		val &= ~(NV_FTR(ISAR1, LS64)	|
 			 NV_FTR(ISAR1, SPECRES));
 		break;