Page and block PTE decoding can share some code. Let's
first handle table PTE and factorize some code shared by
page and block PTEs.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200728150815.11446-2-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>