There's no point looking for the VMA etc.. when we already know
we are going to fail.

This adds some code to set "code" for the si_code but that will
be gone in subsequent patches.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>