runtime: switch cputicks and switchToCrashStack0 on loong64 to regabi

runtime: switch cputicks and switchToCrashStack0 on loong64 to regabi

goos: linux
goarch: loong64
pkg: runtime
cpu: Loongson-3A6000 @ 2500.00MHz
                     |   old.bench   |   new.bench                        |
                     |   sec/op      |   sec/op      vs base              |
SelectUncontended       246.6n ± 0%     247.4n ± 0%  +0.32% (p=0.000 n=10)
SelectSyncContended     1.458µ ± 0%     1.461µ ± 0%  +0.17% (p=0.000 n=10)
SelectAsyncContended    246.6n ± 0%     247.5n ± 0%  +0.36% (p=0.000 n=10)
SelectNonblock          32.81n ± 0%     32.81n ± 0%       ~ (p=1.000 n=10)
SelectProdCons          653.8n ± 0%     652.2n ± 0%  -0.24% (p=0.010 n=10)
GoroutineSelect         2.204m ± 0%     2.172m ± 0%  -1.46% (p=0.000 n=10)
GoroutineForRange       1.775m ± 0%     1.748m ± 0%  -1.54% (p=0.000 n=10)
geomean                 3.573µ          3.561µ       -0.34%

Change-Id: I6337cad72369e77e378b6e9bec6521d71b3f4fc5
Reviewed-on: https://go-review.googlesource.com/c/go/+/610175
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tim King <taking@google.com>