Revert "runtime: convert ncgocall to atomic type"

This reverts CL 426075.

Reason for revert: Import missing from cgocall.go.

Change-Id: Iac17e914045b83da30484dbe2a624cde526fb175
Reviewed-on: https://go-review.googlesource.com/c/go/+/427614
Reviewed-by: Heschi Kreinick <heschi@google.com>

src/runtime/cgocall.go

@@ -111,7 +111,7 @@ func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr {
 	return as.retval
 }
 
-var ncgocall atomic.Uint64 // number of cgo calls in total for dead m
+var ncgocall uint64 // number of cgo calls in total for dead m
 
 // Call from Go to C.
 //

src/runtime/debug.go

@@ -45,7 +45,7 @@ func NumCPU() int {
 
 // NumCgoCall returns the number of cgo calls made by the current process.
 func NumCgoCall() int64 {
-	var n = int64(ncgocall.Load())
+	var n = int64(atomic.Load64(&ncgocall))
 	for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
 		n += int64(mp.ncgocall)
 	}

src/runtime/proc.go

@@ -1530,7 +1530,7 @@ found:
 	}
 	unlock(&sched.lock)
 
-	ncgocall.Add(int64(mp.ncgocall))
+	atomic.Xadd64(&ncgocall, int64(mp.ncgocall))
 
 	// Release the P.
 	handoffp(releasep())