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

arch/arm64/include/asm/pgtable-hwdef.h

@@ -190,7 +190,6 @@
  * Memory Attribute override for Stage-2 (MemAttr[3:0])
  */
 #define PTE_S2_MEMATTR(t)	(_AT(pteval_t, (t)) << 2)
-#define PTE_S2_MEMATTR_MASK	(_AT(pteval_t, 0xf) << 2)
 
 /*
  * EL2/HYP PTE/PMD definitions