platform/x86: intel/pmc: Fix ioremap() of bad address

platform/x86: intel/pmc: Fix ioremap() of bad address

In pmc_core_ssram_get_pmc(), the physical addresses for hidden SSRAM
devices are retrieved from the MMIO region of the primary SSRAM device.
If additional devices are not present, the address returned is zero.
Currently, the code does not check for this condition, resulting in
ioremap() incorrectly attempting to map address 0.

Add a check for a zero address and return 0 if no additional devices
are found, as it is not an error for the device to be absent.

Fixes: a01486dc4bb1 ("platform/x86/intel/pmc: Cleanup SSRAM discovery")
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20250106174653.1497128-1-david.e.box@linux.intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>