coresight: etx4x: sysfs: fix spinlock unlock issue

If an error is detected in addr_range_show() or addr_range_store(),
need to unlock spinlock and then return.

Change-Id: I84be54a1906fd3a9d5f24946a7941e87595e95c1
Signed-off-by: Yuanfang Zhang <zhangyuanfang@codeaurora.org>