soc: imx: imx8mp-blk-ctrl: handle PCIe PHY resets

Dessert the PHY reset when powering up the domain and put it back
into reset when the domain is powered down.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>