target/rx: TCG helpers

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
[PMD: Removed tlb_fill, extracted from patch of Yoshinori Sato
 'Convert to CPUClass::tlb_fill']
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200224141923.82118-6-ysato@users.sourceforge.jp>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>