Revision 324341

Tag all armv7 kernels as such in their machine config line.

Transition all boards that support arm cortex CPUs to armv7. This
leaves two armv6 kernels in the tree. RPI-B, which uses the BCM2835
which has a ARM1176 core, and VERSATILEPB, which is a qemu board setup
around the time RPI-B went in. Copy std.armv6 to std.armv7, even
though that duplicates a lot of stuff. More work needs to be done to
sort out the duplication.

Differential Revision: https://reviews.freebsd.org/D12027