dl2k: nulify fraginfo after unmap
dl2k: nulify fraginfo after unmap

Patch fixes: "DMA-API: device driver tries to free an invalid DMA
memory address" warning reported here:
https://bugzilla.redhat.com/show_bug.cgi?id=639824

Reported-by: Frantisek Hanzlik <e4201531576767a8ec1d7505b3469aeade94ed61@hanzlici.cz>
Signed-off-by: Stanislaw Gruszka <1542dc81552e668e197a396f69e655c1621c300d@redhat.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs