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

In the Linux kernel, the following vulnerability has been resolved:

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.