platform/x86/intel/pmc: Fix in pmc_core_ssram_get_pmc()

platform/x86/intel/pmc: Fix in pmc_core_ssram_get_pmc()

Passing PMC_IDX_MAIN in pmc_core_pmc_add() adds only primary pmc to pmcdev.
Use pmc_idx instead to add all available pmcs.

Fixes: a01486dc4bb1 ("platform/x86/intel/pmc: Cleanup SSRAM discovery")
Signed-off-by: Rajvi Jingar <rajvi.jingar@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20231216011702.1976408-1-rajvi.jingar@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>