I ran into occasional BUGs in scatterlist.h, which turned
out the be caused by accessing an uninitialized scatterlist
entry from eseqiv. I'm not sure whether this patch is correct
since I'm seeing invalid packets with and without this patch
(probably related to HIFN though) and I don't understand why
scatterwalk_sg_next() returns either a scatterlist or a
struct page dependant on the length, but at least it fixes
the BUG() for me :)