tcg: move tb_ctx.tb_phys_invalidate_count to tcg_ctx

Thereby making it per-TCGContext. Once we remove tb_lock, this will
avoid an atomic increment every time a TB is invalidated.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/exec/tb-context.h

@@ -37,7 +37,6 @@ struct TBContext {
 
     /* statistics */
     unsigned tb_flush_count;
-    int tb_phys_invalidate_count;
 };
 
 extern TBContext tb_ctx;