We'd like to move disas.c into the common code source set, where
CONFIG_USER_ONLY is not available anymore. So we have to move
the related code into a separate file instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230508133745.109463-2-thuth@redhat.com>
[rth: Type change done in a separate patch]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>