mtd: spi-nor: hisi-sfc: Put child node np on error path

Put the child node np when it fails to get or register device.

Fixes: e523f111 ("mtd: spi-nor: add hisilicon spi-nor flash controller driver")
Cc: stable@vger.kernel.org
Signed-off-by: Pan Bian <bianpan2016@163.com>
[ta: Add Fixes tag and Cc stable]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20210121091847.85362-1-bianpan2016@163.com