platform/x86/amd/pmc: Detect when STB is not available

platform/x86/amd/pmc: Detect when STB is not available

Loading the amd_pmc module as:

    amd_pmc enable_stb=1

...can result in the following messages in the kernel ring buffer:

    amd_pmc AMDI0009:00: SMU cmd failed. err: 0xff
    ioremap on RAM at 0x0000000000000000 - 0x0000000000ffffff
    WARNING: CPU: 10 PID: 2151 at arch/x86/mm/ioremap.c:217 __ioremap_caller+0x2cd/0x340

Further debugging reveals that this occurs when the requests for
S2D_PHYS_ADDR_LOW and S2D_PHYS_ADDR_HIGH return a value of 0,
indicating that the STB is inaccessible. To prevent the ioremap
warning and provide clarity to the user, handle the invalid address
and display an error message.

Link: https://lore.kernel.org/platform-driver-x86/c588ff5d-3e04-4549-9a86-284b9b4419ba@amd.com
Fixes: 3d7d407dfb05 ("platform/x86: amd-pmc: Add support for AMD Spill to DRAM STB feature")
Acked-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Corey Hickey <bugfood-c@fatooh.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20241028180241.1341624-1-bugfood-ml@fatooh.org
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>