x86/events/amd/iommu: Declare pr_fmt() format

x86/events/amd/iommu: Declare pr_fmt() format

Declare pr_fmt() format for perf/amd_iommu and remove unnecessary
pr_debug() calls.

Also check return value when _init_events_attrs() fails and issue an
error message.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jörg Rödel <joro@8bytes.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: iommu@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/1487926102-13073-2-git-send-email-Suravee.Suthikulpanit@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>