reset: imx7: Fix the iMX8MP PCIe PHY PERST support

reset: imx7: Fix the iMX8MP PCIe PHY PERST support

On i.MX7/iMX8MM/iMX8MQ, the initialized default value of PERST bit(BIT3)
of SRC_PCIEPHY_RCR is 1b'1.
But i.MX8MP has one inversed default value 1b'0 of PERST bit.

And the PERST bit should be kept 1b'1 after power and clocks are stable.
So fix the i.MX8MP PCIe PHY PERST support here.

Fixes: e08672c03981 ("reset: imx7: Add support for i.MX8MP SoC")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Marek Vasut <marex@denx.de>
Tested-by: Richard Leitner <richard.leitner@skidata.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/1661845564-11373-5-git-send-email-hongxing.zhu@nxp.com