hw/i386: changes towards enabling -Wshadow=local for x86 machines

hw/i386: changes towards enabling -Wshadow=local for x86 machines

Code changes that addresses all compiler complaints coming from enabling
-Wshadow flags. Enabling -Wshadow catches cases of local variables shadowing
other local variables or parameters. These makes the code confusing and/or adds
bugs that are difficult to catch.

See also

   Subject: Help wanted for enabling -Wshadow=local
   Message-Id: <87r0mqlf9x.fsf@pond.sub.org>
   https://lore.kernel.org/qemu-devel/87r0mqlf9x.fsf@pond.sub.org

CC: Markus Armbruster <armbru@redhat.com>
CC: Philippe Mathieu-Daude <philmd@linaro.org>
CC: mst@redhat.com
Signed-off-by: Ani Sinha <anisinha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-ID: <20231003102803.6163-1-anisinha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>