Add ARMV6 as an arm option.  This will cause obscure magic in config(8)
to automatically set the armv6 option when MACHINE_ARCH is armv6.  That
allows replacing ever-growing lists of cpu names as options to compile
a given file with the using either "optional armv6" or "optional !armv6".


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274937 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f