sched/deadline: Clarify nanoseconds in uapi

Specify the time values of the deadline parameters of deadline,
runtime, and period as being in nanoseconds explicitly as they always
have been.

Signed-off-by: Christian Loehle <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Acked-by: Juri Lelli <[e-mail]>
Acked-by: Rafael J. Wysocki <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

include/uapi/linux/sched/types.h

···
  *
  * This is reflected by the following fields of the sched_attr structure:
  *
- *  @sched_deadline	representative of the task's deadline
- *  @sched_runtime	representative of the task's runtime
- *  @sched_period	representative of the task's period
+ *  @sched_deadline	representative of the task's deadline in nanoseconds
+ *  @sched_runtime	representative of the task's runtime in nanoseconds
+ *  @sched_period	representative of the task's period in nanoseconds
  *
  * Given this task model, there are a multiplicity of scheduling algorithms
  * and policies, that can be used to ensure all the tasks will make their