rtla: Add optional dependency on libcpupower

If libcpupower is present, set HAVE_LIBCPUPOWER_SUPPORT macro to allow
features depending on libcpupower in rtla.

Link: https://lore.kernel.org/20241017140914.3200454-3-tglozar@redhat.com


Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>