exec: Rename guest_{addr,range}_valid to *_untagged

The places that use these are better off using untagged
addresses, so do not provide a tagged versions.  Rename
to make it clear about the address type.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210212184902.1251044-16-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>