perf vender events arm64: Use "Topdown" as topdown metric group name

HiSilicon HIP08 does support Topdown metrics but perf tool complains
when trying to count Topdown metrics:
[root@localhost tracing]# perf stat --topdown
Topdown requested but the topdown metric groups aren't present.
(See perf list the metric groups have names like TopdownL1)

It's because tool's using "Topdown" as the metric group name[1] rather
than "TopDown", so follow the convention. This is introduced by [2]
which allows to use json metrics to support --topdown function.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/builtin-stat.c?h=v6.11-rc1#n1994


[2] commit 1647cd5b ("perf stat: Implement --topdown using json metrics")

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Cc: prime.zeng@hisilicon.com
Cc: hejunhao3@huawei.com
Cc: linuxarm@huawei.com
Cc: shameerali.kolothum.thodi@huawei.com
Link: https://lore.kernel.org/r/20240912063903.31460-1-yangyicong@huawei.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>