Fix s390x build failure by removing golang.org/x/sys

This fix tries to fix the issue raised in #24168 where
golang.org/x/sys causes s390x build failure.

This fix removed the import of "golang.org/x/sys/unix".

This fix fixes #24168.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

pkg/sysinfo/numcpu_linux.go

@@ -6,8 +6,6 @@ import (
 	"runtime"
 	"syscall"
 	"unsafe"
-
-	"golang.org/x/sys/unix"
 )
 
 // numCPU queries the system for the count of threads available
@@ -17,10 +15,10 @@ import (
 // Returns 0 on errors. Use |runtime.NumCPU| in that case.
 func numCPU() int {
 	// Gets the affinity mask for a process: The very one invoking this function.
-	pid, _, _ := syscall.RawSyscall(unix.SYS_GETPID, 0, 0, 0)
+	pid, _, _ := syscall.RawSyscall(syscall.SYS_GETPID, 0, 0, 0)
 
 	var mask [1024 / 64]uintptr
-	_, _, err := syscall.RawSyscall(unix.SYS_SCHED_GETAFFINITY, pid, uintptr(len(mask)*8), uintptr(unsafe.Pointer(&mask[0])))
+	_, _, err := syscall.RawSyscall(syscall.SYS_SCHED_GETAFFINITY, pid, uintptr(len(mask)*8), uintptr(unsafe.Pointer(&mask[0])))
 	if err != 0 {
 		return 0
 	}