libnvdimm: Remove duplicate struct declaration

struct device is declared at 133rd line. The second declaration is
unnecessary, remove it.

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Link: https://lore.kernel.org/r/20210419112725.42145-1-wanjiabing@vivo.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>