coresight: tmc: Decouple the perf buffer allocation from sysfs mode

coresight: tmc: Decouple the perf buffer allocation from sysfs mode

Currently the perf buffer allocation follows the below logic:
- if the required AUX buffer size if larger, allocate the buffer with
  the required size
- otherwise allocate the size reference to the sysfs buffer size

This is not useful as we only collect to one AUX data, so just try to
allocate the buffer match the AUX buffer size.

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/df8967cd-2157-46a2-97d9-a1aea883cf63@arm.com/
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Junhao He <hejunhao3@h-partners.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260121101543.2017014-4-wangyushan12@huawei.com