Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC r261982, r261987, r262123, r262244, r262278, r262280, r262353, r262354,
r262355, r262419,

Add Vybrid driver for Synchronous Audio Interface (SAI).

Decrease SAI buffer size. Handle eDMA interrupt on running channel only.

Give the physmem fdt helper routines static linkage since no global
definition of them is provided anywhere.

Add imx6 early printf support, wrapped in #if 0 because it's rarely needed.

Add basic cpu frequency control and temperature monitoring to imx6_anatop.

Add the FREEBSD_BOOT_LOADER option so that a loaded DTB passed in from
ubldr will actually get used.

Create a generic IMX6 kernel config, then fix it to have an ident line.

Don't force imx6 bootverbose on anymore, it can be set from ubldr now.

MFC r257453: Add stubbed-out imx6 support for clocks and power management.

Add stubbed-out imx6 support for clocks and power management. This
contains little more than a few stub functions required to keep the
linker happy, but it's enough to let early imx6 development proceed.