x86/CPU/AMD: Only apply Zenbleed fix for Zen2 during late microcode load

Commit

  f69759be ("x86/CPU/AMD: Move Zenbleed check to the Zen2 init function")

causes a bit in the DE_CFG MSR to get set erroneously after a microcode late
load.

The microcode late load path calls into amd_check_microcode() and subsequently
zen2_zenbleed_check(). Since the above commit removes the cpu_has_amd_erratum()
call from zen2_zenbleed_check(), this will cause all non-Zen2 CPUs to go
through the function and set the bit in the DE_CFG MSR.

Call into the Zenbleed fix path on Zen2 CPUs only.

  [ bp: Massage commit message, use cpu_feature_enabled(). ]

Fixes: f69759be ("x86/CPU/AMD: Move Zenbleed check to the Zen2 init function")
Signed-off-by: John Allen <john.allen@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20240923164404.27227-1-john.allen@amd.com

arch/x86/kernel/cpu/amd.c

@@ -1202,5 +1202,6 @@ void amd_check_microcode(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 		return;
 
+	if (cpu_feature_enabled(X86_FEATURE_ZEN2))
 		on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }