clk: Move allwinner driver into the common directory

No need to keep it under sys/arm/allwinner/clkng
It's easier to find which controller we support by looking under one directory.
It will also be shared with Allwinner RiscV SoC.

Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D43188

sys: Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

aw_ccung: Add a10/a20 support

Note: At this time, this has only been tested on a single board from one of
the supported SoCs. This is enough to boot the board from MMC and have
functional USB- which is still an improvement over where we were at just
before with no functional clocks.

Differential Revision: https://reviews.freebsd.org/D15810

Allwinner: Move a10_padconf.c into a10 subdirectory.

Rename kernel config A10 into ALLWINNER_UP as it is intend to work with all
Allwinner Uniprocessor SoC.
As of now it works with A10 and A13 (and possibly R8 as it is the same as the A13).
Move files.a10 into a1o subdirectory as it should be.
Rename std.a10 into std.allwinner_up