coresight: core: Fix use of uninitialized pointer

coresight: core: Fix use of uninitialized pointer

Currently the pointer "sink" might be checked before initialized. Fix
this by initializing this pointer.

Link: https://lore.kernel.org/r/1620912469-52222-2-git-send-email-liuqi115@huawei.com
Fixes: 6d578258b955 ("coresight: Make sysfs functional on topologies with per core sink")
Signed-off-by: Junhao He <hejunhao2@hisilicon.com>
Signed-off-by: Qi Liu <liuqi115@huawei.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210614175901.532683-3-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>