Before recent commit abc9bf69, configure_icount() returned early
when option "shift" was absent: succeed when option "align" was also
absent, else fail.

Since then, it still errors out when only "align" is present, but
continues when both are absent.  Crashes when examining the value of
"shift" further.  Reproducer: -icount "".

Revert this erroneous part of the commit.

Fixes: abc9bf69
Fixes: Coverity CID 1428754
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200515042231.18201-1-armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>