Add uclampset schedutil

Add uclampset schedutil

Utilization clamping is a new kernel feature that got merged in 5.3. It
allows controlling the performance of a process by manipulating the
utilization such that the task appears bigger or smaller than what it
really is.

There's a system-wide control to to restrict what maximum values the
process are allowed to use.

Man page added in a later patch attempts to explain the usage in more
detail.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>