powercap: intel_rapl_tpmi: Fix System Domain probing

Only domain root packages can enumerate System (Psys) domain.
Whether a package is domain root or not is described in the Bit 0 of the
Domain Info register.

Add support for Domain Info register and fix the System domain probing
accordingly.

Fixes: 9eef7f9d ("powercap: intel_rapl: Introduce RAPL TPMI interface driver")
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Cc: 6.5+ <stable@vger.kernel.org> # 6.5+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>