dashboard: more subrepo linux-mipsle-mengzhuo test

The Loongson 3A4000 is out performance other mips
machine, we can run more sub-repo testes.

Change-Id: Ic2ae8f582174ad4ed7815ffdf92665cfe5071d74
Reviewed-on: https://go-review.googlesource.com/c/build/+/378534
Trust: Zhuo Meng <mzh@golangcn.org>
Run-TryBot: Zhuo Meng <mzh@golangcn.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

dashboard/builders.go

@@ -2491,9 +2491,8 @@ func init() {
 		FlakyNet:       true,
 		HostType:       "host-linux-mipsle-mengzhuo",
 		Name:           "linux-mips64le-mengzhuo",
-		SkipSnapshot:   true,
+		buildsRepo:     onlyMasterDefault,
 		distTestAdjust: mipsDistTestPolicy,
-		buildsRepo:     mipsBuildsRepoPolicy,
 	})
 	addBuilder(BuildConfig{
 		FlakyNet:       true,