Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add Allwinner A20 HDMI support.

The HDMI driver will attach a framebuffer device when a display is
connected. If the EDID can be read and contains a preferred mode, it
will be used. Otherwise the framebuffer will default to 800x600.

In addition, if the EDID contains a CEA-861 extension block and the
"basic audio" flag is set, audio playback at 48kHz 16-bit stereo is
enabled on the controller.

Reviewed by: andrew
Approved by: gonzo (mentor)
Differential Revision: https://reviews.freebsd.org/D5383

Somewhat improve HDMI event API

- Pass device_t for HDMI framer as an argument for event hook
- Use #define for event values, instead of opaque (and unused) 0

hdmi_if.m will be reused by iMX6 IPU code so move it to arm/arm

Move all HDMI-related stuff to hdmi_if.m, hdmi.h is not required

Add HDMI support to Beaglebone Black:

- Add driver for TDA19988 HDMI framer
- Add simple interface to communicate with HDMI sink: read EDID and set videomode
- Add event-based API to notify LCD controller when HDMI sink is available
- Add HDMI framer node and add refernce to it to lcdc node. This part of
DTS tree is custom and does not match Linux DTS because Linux uses
combination of pseudo-node in DTS and hardcoded driver information
that does not map to our model.