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

Remove the arm KERNPHYSADDR option as it is no longer used. The make
option is still in existance as it is used to build the trampoline code.

Remove STARTUP_PAGETABLE_ADDR from the ARM configs and replace it with
memory at the end of the kernel.

This helps reduce the SoC and board specific configuration required.

Reviewed by: bsdimp
Tested by: jmg (armeb), br

Opt-in rather than opt-out of the SoC. We don't really support
running with multiple SoCs compiled in very well anyway, so this just
wastes space. As more and more SoCs arrive in the tree, it is better
to edit one master file that builds them all than many board files.

Exclude at91sam9x25 support, which just wastes space for Ethernut 5.

Compute the master clock frequency, so we no longer need to have it
compiled into the kernel. This allows us to boot the same kernel on
machines with different master clock frequencies, so long as we can
determine the main clock frequency accurately. Cleanup the pmc clock
init function so it can be called in early boot so we can use the
serial port just after we call cninit.

# We have two calls to at91_pmc_clock_init for reasons unknown, that will
# be fixed later -- it is harmless for now.

Add glue/support for the SAM9XE512-based Ethernut 5 boards. Currently,
all integrated and on-board peripherals except the DataFlash (at91_spi(4)
and at45d(4) still need to be unb0rken) and NAND Flash (missing NAND
framework) are working.
AFAICT, this makes FreeBSD the first operating system besides Nut/OS
supporting Ethernut 5 out of tree.