MFC r312292, r313573:

Stop including sys/types.h from arm's machine/atomic.h, fix the places
where atomic.h was being included without ensuring that types.h (via
param.h) was included first, as required by atomic(9).

Remove arm's cpuconf.h, and references to it, after moving a few lines from
it into pmap-v4.h where they are used. Other than those few lines of
support for different MMU types, nothing in cpuconf.h has been used in our
code for quite a while.
The file existed to set up a variety of symbols to describe the
architecture. Over the past few years we have converted all of our source
to use the new architecture symbols standardized by ARM Inc, and predefined
by both clang and gcc.

MFC r306901:

ARM: Split identify_arm_cpu() into ARMv4 and ARMv6 variant.
On ARMv6, be more verbose about supported CPU features and/or
optional instructions.