KVM: arm64: Drop PTE_S2_MEMATTR_MASK

The only user of PTE_S2_MEMATTR_MASK macro had been removed since
commit a501e324 ("arm64: Clean up the default pgprot setting").
It has been about six years and no one has used it again.

Let's drop it.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200415105746.314-1-yuzenghui@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>