x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails

In the Linux kernel, the following vulnerability has been resolved: x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails In mce_threshold_create_device(), if threshold_create_bank() fails, the previously allocated threshold banks array @bp will be leaked because the call to mce_threshold_remove_device() will not free it. This happens because mce_threshold_remove_device() fetches the pointer through the threshold_banks per-CPU variable but bp is written there only after the bank creation is successful, and not before, when threshold_create_bank() fails. Add a helper which unwinds all the bank creation work previously done and pass into it the previously allocated threshold banks array for freeing. [ bp: Massage. ]