x86/fault: Split the OOPS code out from no_context()

Not all callers of no_context() want to run exception fixups.
Separate the OOPS code out from the fixup code in no_context().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/450f8d8eabafb83a5df349108c8e5ea83a2f939d.1612924255.git.luto@kernel.org