Add imx8mp-libra-fpsc board

Add imx8mp-libra-fpsc board

Add new imx8mp-libra-fpsc board.
Bootph tags as well as USB device tree nodes are in u-boot.dtsi for now
and will be removed when upstreamed.
The Libra i.MX 8M Plus FPSC is a single board computer. It uses an i.MX
8M Plus FPSC [1] System on Module which utilizes the FPSC standard [2].

[1] https://www.phytec.eu/en/produkte/system-on-modules/phycore-imx-8m-plus-fpsc
[2] https://www.phytec.eu/en/produkte/system-on-modules/fpsc

Signed-off-by: Benjamin Hahn <B.Hahn@phytec.de>
Reviewed-by: Teresa Remmet <t.remmet@phytec.de>
Tested-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Yannic Moog <y.moog@phytec.de>