ARM: imx: vining2000: Repair PCIe support

Ever since the conversion to DM PCI, the board was missing the PCIe DT
nodes, hence the PCI did not really work. Fill in the DT nodes and add
missing PCIe device reset.

Moreover, bring the PCIe power domain up before booting Linux. This is
mandatory to keep old broken vendor kernels working, as they do not do
so and depend on the bootloader to bring the power domain up.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Silvio Fricke <silvio.fricke@softing.com>
Cc: Stefano Babic <sbabic@denx.de>