clk: Move clock code in dev/clk

We've removed kernel option EXT_RESOURCES almost two years ago.
While it was ok to have some code under a common 'extres' subdirectory
at first, we now have a lot of consumer of it and we made it mandatory
so no need to have it under a cryptic name.

Reviewed by: mhorne
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D43191

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

arm: Rename hdmi_if.m to crtc_if.m

There is nothing hdmi related in this interface, it's just a generic interface
for crt controller so rename it.
This also remove the 'hdmi' device used in arm kernel config. 'vt' now controls
if we build this interface (sc(4) isn't supported on arm).

Sponsored by: Beckhoff Automation GmbH & Co. KG
Reviewed by: andrew
Differential Revision: https://reviews.freebsd.org/D39120

dwc_hdmi: Remove unused devclass argument to DRIVER_MODULE.

Add support for audio on I2S based DesignWare HDMI controllers.

Relnotes: yes

Split the DesignWare HDMI-specific code from imx6_hdmi.c into a separate
file and add a generic DT binding that takes advantage of the extres
framework for setting up clocks.

Reviewed by: gonzo
Differential Revision: https://reviews.freebsd.org/D8826