x86/amd_node: Update __amd_smn_rw() error paths

Use guard(mutex) and convert PCI error codes to common ones.

Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-12-yazen.ghannam@amd.com