Fix hgatp CSR write

The write mask is incorrectly computed by hgatp_csr_t::unlogged_write()
which leads to hgatp.PPN bits not getting updated upon hgatp CSR write.

This patch fixes hgatp CSR writes and gets KVM RISC-V working again
on Spike.

Fixes: 70b7e9ca2d ("mmu: support asid/vmid (#928)")
Signed-off-by: Anup Patel <anup@brainfault.org>

riscv/csrs.cc

@@ -978,7 +978,7 @@ bool hgatp_csr_t::unlogged_write(const reg_t val) noexcept {
         proc->supports_impl(IMPL_MMU_VMID) ? HGATP32_VMID : 0;
   } else {
     mask = (HGATP64_PPN & ((reg_t(1) << (MAX_PADDR_BITS - PGSHIFT)) - 1)) |
-        proc->supports_impl(IMPL_MMU_VMID) ? HGATP64_VMID : 0;
+        (proc->supports_impl(IMPL_MMU_VMID) ? HGATP64_VMID : 0);
 
     if (get_field(val, HGATP64_MODE) == HGATP_MODE_OFF ||
         (proc->supports_impl(IMPL_MMU_SV39) && get_field(val, HGATP64_MODE) == HGATP_MODE_SV39X4) ||