target/riscv: Use TB_FLAGS_MSTATUS_FS for floating point

Use the TB_FLAGS_MSTATUS_FS macro when enabling floating point in the tb
flags.

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

target/riscv/cpu.h

@@ -301,7 +301,7 @@ static inline void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
 #else
     *flags = cpu_mmu_index(env, 0);
     if (riscv_cpu_fp_enabled(env)) {
-        *flags |= env->mstatus & MSTATUS_FS;
+        *flags |= TB_FLAGS_MSTATUS_FS;
     }
 #endif
 }