MFC r342924, r343749-r343750, r343874, r344893-r344895, r345711

r342924:
dtb: allwinner: Add orangepi-pc to the build

PR: 226011
Submitted by: Greg V <greg@unrelenting.technology>

r343749:
release: arm64: rpi3: Install the RPI3B+ DTB file

We should use the correct DTB file otherwise the firmware uses
the RPI3B one.

r343750:
release: arm64: pine64-lts: Use the newly created u-boot-pine64-lts port

In U-Boot 2019.01 there is now a config for this board, use it for the
release image.

r343874:
mtree: Add dtb subdir to the mtree file

makefs will fails otherwise

Reported by: emaste

r344893:
arm: allwinner: Fix NM clock recalc

If the NM clock is using a fractional divider the formula isn't the same.

r344894:
arm64: allwinner: Add CCU DE2

The Display Engine 2 have it's own Clock and Control Unit, add support
for it.

r344895:
arm64: allwinner: a64: Add TCON clock

The tcon clock need a mux table for it's parent, for now just
list the parents twice.

r345711:
arm: allwinner: clk: Fix nm_recalc

When comparing best frequencies use the absolute value.
If we do not do that we end up choosing an always lower value than
the best one if the exact freq cannot be met.