perf auxtrace arm: Support compat_auxtrace_mmap__{read_head|write_tail}

perf auxtrace arm: Support compat_auxtrace_mmap__{read_head|write_tail}

When the tool runs with compat mode on Arm platform, the kernel is in
64-bit mode and user space is in 32-bit mode; the user space can use
instructions "ldrd" and "strd" for 64-bit value atomicity.

This patch adds compat_auxtrace_mmap__{read_head|write_tail} for arm
building, it uses "ldrd" and "strd" instructions to ensure accessing
atomicity for aux head and tail.  The file arch/arm/util/auxtrace.c is
built for arm and arm64 building, these two functions are not needed for
arm64, so check the compiler macro "__arm__" to only include them for
arm building.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: James Clark <james.clark@arm.com>
Tested-by: James Clark <james.clark@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Russell King (oracle)" <linux@armlinux.org.uk>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lore.kernel.org/lkml/20210829102238.19693-3-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>