soc: imx: imx8mp-blk-ctrl: don't set power device name

Setting the device name after it has been registered confuses the sysfs
cleanup paths. This has already been fixed for the imx8m-blk-ctrl driver in
b64b46fb ("Revert "soc: imx: imx8m-blk-ctrl: set power device name""),
but the same problem exists in imx8mp-blk-ctrl.

Fixes: 556f5cf9 ("soc: imx: add i.MX8MP HSIO blk-ctrl")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>