various: Remove unnecessary OBJECT() cast

The OBJECT() macro is defined as:

  #define OBJECT(obj) ((Object *)(obj))

Remove the unnecessary OBJECT() casts when we already know the
pointer is of Object type.

Patch created mechanically using spatch with this script:

  @@
  typedef Object;
  Object *o;
  @@
  -   OBJECT(o)
  +   o

Acked-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: John Snow <jsnow@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200512070020.22782-3-f4bug@amsat.org>
[Trivial rebase conflict in hw/s390x/sclp.c resolved]