perf/x86/amd/power: Do not load AMD power module on !AMD platforms

The AMD power module can be loaded on non AMD platforms, but unload fails
with the following Oops:

 BUG: unable to handle kernel NULL pointer dereference at           (null)
 IP: __list_del_entry_valid+0x29/0x90
 Call Trace:
  perf_pmu_unregister+0x25/0xf0
  amd_power_pmu_exit+0x1c/0xd23 [power]
  SyS_delete_module+0x1a8/0x2b0
  ? exit_to_usermode_loop+0x8f/0xb0
  entry_SYSCALL_64_fastpath+0x20/0x83

Return -ENODEV instead of 0 from the module init function if the CPU does
not match.

Fixes: c7ab62bf ("perf/x86/amd/power: Add AMD accumulated power reporting mechanism")
Signed-off-by: Xiao Liang <xiliang@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180122061252.6394-1-xiliang@redhat.com

arch/x86/events/amd/power.c

@@ -277,7 +277,7 @@ static int __init amd_power_pmu_init(void)
 	int ret;
 
 	if (!x86_match_cpu(cpu_match))
-		return 0;
+		return -ENODEV;
 
 	if (!boot_cpu_has(X86_FEATURE_ACC_POWER))
 		return -ENODEV;