hw_random: make buffer usable in scatterlist.
virtio_rng feeds the randomness buffer handed by the core directly into the scatterlist, since commit bb347d98 . However, if CONFIG_HW_RANDOM=m, the static buffer isn't a linear address (at least on most archs). We could fix this in virtio_rng, but it's actually far easier to just do it in the core as virtio_rng would have to allocate a buffer every time (it doesn't know how much the core will want to read). Reported-by: Aurelien Jarno <email@example.com> Tested-by: Aurelien Jarno <firstname.lastname@example.org> Signed-off-by: Rusty Russell <email@example.com> Cc: firstname.lastname@example.org