uclampset: Remove validation logic

uclampset: Remove validation logic

While experimenting with a potential extension to uclamp; I realized
I had to modify uclampset to be able to use this extension, which is not
scalable.

Since the syscall will do checks anyway, drop the validation logic and
let the kernel do its work without duplication that can potentially get
stale.

Use more magic value for NOT_SET define. We do have uclamp_set_set flag
to verify if the value is valid anyway, so this is extra paranoia.

Signed-off-by: Qais Yousef <qyousef@layalina.io>