platform/x86/amd/pmc: Propagate SMU errors and validate S2D address

In the Linux kernel, the following vulnerability has been resolved: platform/x86/amd/pmc: Propagate SMU errors and validate S2D address amd_stb_s2d_init() discards the return value of several S2D SMU commands. When the SMU refuses a command (e.g. "SMU cmd failed. err: 0xff") the failure is only noticed indirectly - if at all - and reported as -EIO, masking the real error. More seriously, the S2D_PHYS_ADDR_LOW/HIGH return values are ignored, so on failure phys_addr_low/hi are left uninitialised and the assembled address is passed straight to devm_ioremap(). When the SMU leaves them at zero this maps physical address 0 and trips the ioremap-on-RAM warning: amd_pmc AMDI000B:00: SMU cmd failed. err: 0xff ioremap on RAM at 0x0000000000000000 - 0x0000000000ffffff WARNING: CPU: 13 PID: 4592 at arch/x86/mm/ioremap.c:... Check the return value of each SMU command and propagate it, and reject a zero physical address before calling devm_ioremap().