target/riscv: Allow enabling the Hypervisor extension

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

target/riscv/cpu.h

@@ -258,6 +258,7 @@ typedef struct RISCVCPU {
         bool ext_c;
         bool ext_s;
         bool ext_u;
+        bool ext_h;
         bool ext_counters;
         bool ext_ifencei;
         bool ext_icsr;