MFC r358407:

Merge r358406 from the clang1000-import branch:

Fix the following -Werror warning from clang 10.0.0:

sys/arm/arm/identcpu-v6.c:227:5: error: misleading indentation; statement is not part of the previous 'if' [-Werror,-Wmisleading-indentation]
if (val & CPUV7_CT_CTYPE_RA)
^
sys/arm/arm/identcpu-v6.c:225:4: note: previous statement is here
if (val & CPUV7_CT_CTYPE_WB)
^

This was due to an accidentally inserted tab before the if statement.

MFC r320001 by zbb:

Fix typo in "Marvell" string

Change Marwell to Marvell

Pointed out by: Ravi Pokala <rpokala@mac.com>
Sponsored by: Rubicon Communications, LLC (Netgate)

MFC r329989, r330044

r329989:
Add support for booting into kdb on arm platforms when the RB_KDB is set
(using "boot -d" at the loader propmt or setting boot_ddb in loader.conf).

Submitted by: Thomas Skibo <thomasskibo@yahoo.com>
Differential Revision: https://reviews.freebsd.org/D14428

r330044:
Add a hw.model sysctl oid for armv6/7 which reports the CPU model, similar
to what other arches (all except riscv and armv4/5) do.

Submitted by: Hyun Hwang <hyun@caffeinated.codes>
Differential Revision: https://reviews.freebsd.org/D14465

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.