powercap: intel_rapl: Remove redundant cpu parameter

For rapl_packages that rely on online CPUs to work, rp->lead_cpu always
has a valid CPU id.

Remove the redundant cpu parameter in rapl_check_domain(),
rapl_detect_domains() and .check_unit() callbacks.

No functional change.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wang Wendy <wendy.wang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>