systemtap: Fix task_work_cancel build

systemtap: Fix task_work_cancel build

Backport a patch to fix:
 107 |         twork = task_work_cancel(task, func);
      |                                        ^~~~
      |                                        |
      |                                        task_work_func_t {aka void (*)(struct callback_head *)}
/work/rad/wrs/wrl-systemtap-demo/qemux86-64-std-23p17/build/tmp-glibc/work/x86_64-linux/systemtap-native/4.8-r0/recipe-sysroot-native/usr/share/systemtap/runtime/stp_task_work.c:107:40: note: expected 'struct callback_head *' but argument is of type 'task_work_func_t' {aka 'void (*)(struct callback_head *)'}
/work/rad/wrs/wrl-systemtap-demo/qemux86-64-std-23p17/build/tmp-glibc/work/x86_64-linux/systemtap-native/4.8-r0/recipe-sysroot-native/usr/share/systemtap/runtime/stp_task_work.c:13:26: error: incompatible types when assigning to type 'struct callback_head *' from type 'bool' {aka '_Bool'}
   13 | #define task_work_cancel (* (task_work_cancel_fn)kallsyms_task_work_cancel)
      |                          ^
/work/rad/wrs/wrl-systemtap-demo/qemux86-64-std-23p17/build/tmp-glibc/work/x86_64-linux/systemtap-native/4.8-r0/recipe-sysroot-native/usr/share/systemtap/runtime/stp_task_work.c:107:17: note: in expansion of macro 'task_work_cancel'
  107 |         twork = task_work_cancel(task, func);
      |                 ^~~~~~~~~~~~~~~~

Signed-off-by: Jinfeng Wang <jinfeng.wang.cn@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>