perf: arm_cspmu: fix error handling in arm_cspmu_impl_unregister()

driver_find_device() calls get_device() to increment the reference
count once a matching device is found. device_release_driver()
releases the driver, but it does not decrease the reference count that
was incremented by driver_find_device(). At the end of the loop, there
is no put_device() to balance the reference count. To avoid reference
count leakage, add put_device() to decrease the reference count.

Found by code review.

Cc: [e-mail]
Fixes: bfc653aa89cb ("perf: arm_cspmu: Separate Arm and vendor module")
Signed-off-by: Ma Ke <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>

drivers/perf/arm_cspmu/arm_cspmu.c

···
 
 	/* Unbind the driver from all matching backend devices. */
 	while ((dev = driver_find_device(&arm_cspmu_driver.driver, NULL,
-			match, arm_cspmu_match_device)))
+			match, arm_cspmu_match_device))) {
 		device_release_driver(dev);
+		put_device(dev);
+	}
 
 	mutex_lock(&arm_cspmu_lock);