drivers/perf: convert sysfs scnprintf family to sysfs_emit_at() and sysfs_emit()

Use the generic sysfs_emit_at() and sysfs_emit() function to take place
of scnprintf()

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Link: https://lore.kernel.org/r/1616148273-16374-3-git-send-email-liuqi115@huawei.com


Signed-off-by: Will Deacon <will@kernel.org>