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fpga_region_class_find() in fpga_region_test_class_find() will call
get_device() if the data is matched, which will increment refcount for
dev->kobj, so it should call put_device() to decrement refcount for
dev->kobj to free the region, because fpga_region_unregister() will call
fpga_region_dev_release() only when the refcount for dev->kobj is zero
but fpga_region_test_init() call device_register() in
fpga_region_register_full(), which also increment refcount.

So call put_device() after calling fpga_region_class_find() in
fpga_region_test_class_find(). After applying this patch, the following
memory leak is never detected.

unreferenced object 0xffff88810c8ef000 (size 1024):
  comm "kunit_try_catch", pid 1875, jiffies 4294715298 (age 836.836s)
  hex dump (first 32 bytes):
    b8 d1 fb 05 81 88 ff ff 08 f0 8e 0c 81 88 ff ff  ................
    08 f0 8e 0c 81 88 ff ff 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff817ebad7>] km...