x86/unwind/orc: Silence warnings caused by missing ORC data

The ORC unwinder attempts to fall back to frame pointers when ORC data
is missing for a given instruction.  It sets state->error, but then
tries to keep going as a best-effort type of thing.  That may result in
further warnings if the unwinder gets lost.

Until we have some way to register generated code with the unwinder,
missing ORC will be expected, and occasionally going off the rails will
also be expected.  So don't warn about it.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Ivan Babrou <ivan@cloudflare.com>
Link: https://lkml.kernel.org/r/06d02c4bbb220bd31668db579278b0352538efbb.1612534649.git.jpoimboe@redhat.com