arm: dts: imx6q: Add Linux dts files for Phytec Mira

Add Phytec Mira device tree files, for use with pcm058.
>From Linux 5.6, commit 7111951b8d49 upstream

Signed-off-by: Niel Fourie <lusus@denx.de>
Cc: Stefano Babic <sbabic@denx.de>