PCI: imx6: Move regulator enable out of imx6_pcie_deassert_core_reset()

Move regulator enable out of imx6_pcie_deassert_core_reset(), since the
regulator_enable() has nothing to do with imx6_pcie_deassert_core_reset().

Link: https://lore.kernel.org/r/1657783869-19194-12-git-send-email-hongxing.zhu@nxp.com
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>