sw64: maintain PMU counter usage status with bitmap

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56X48



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It's easier to manage usage status of performance counters with
bitmap operations, and this patch removes some data structures
that are no longer needed.

Signed-off-by: He Chuyue <hechuyue@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>