CVE-2025-21913 x86/amd_nb: Use rdmsr_safe() in amd_get_mmconfig_range()

In the Linux kernel, the following vulnerability has been resolved: x86/amdnb: Use rdmsrsafe in amdgetmmconfigrange Xen doesn't offer MSRFAM10HMMIOCONFBASE to all guests. This results in the following warning: unchecked MSR access error: RDMSR from 0xc0010058 at rIP: 0xffffffff8101d19f...