ARM: dts: imx: Enable PCIe and NVMe on Data Modul i.MX8M Mini eDM SBC

ARM: dts: imx: Enable PCIe and NVMe on Data Modul i.MX8M Mini eDM SBC

Enable PCIe/NVMe support on Data Modul i.MX8M Mini eDM SBC. Except for
the configuration options which are enabled, add slight adjustment
to board u-boot.dtsi, which is necessary as there is currently no
driver for the I2C PCIe clock generator. Since the generator is
strapped to be always on, it is possible to supplant the generator
functionality by fixed-clock.

Signed-off-by: Marek Vasut <marex@denx.de>