libprocessgroup: ensure schedboost_enabled is true with uclamp

In the current state, schedboost_enabled() is true if and only if
schedtune is in use. As a result, all tests conditioned by
schedboost_enabled() will be skipped on devices using uclamp since it is
and extension of the CPU controller.

Fix this by making schedboost_enabled() return true if either schedtune
or the CPU controller is enabled.

Bug: 44953631
Change-Id: Idaadf252c9cf411a176180ab8988d559ca8a1332
Signed-off-by: Quentin Perret <qperret@google.com>