monitor/hmp-cmds: Remove redundant statement in hmp_rocker_of_dpa_groups()

monitor/hmp-cmds: Remove redundant statement in hmp_rocker_of_dpa_groups()

Clang static code analyzer show warning:
monitor/hmp-cmds.c:2867:17: warning: Value stored to 'set' is never read
                set = true;
                ^     ~~~~

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200302130715.29440-14-kuhn.chenqun@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>