sg: add missing sg_init_table calls to zfcp

kernel BUG at include/linux/scatterlist.h:50!
illegal operation: 0001 [#1]
[...]
Call Trace:
([<000000000026f184>] zfcp_ns_gid_pn_request+0x4c/0x2a0)
 [<0000000000276dd4>] zfcp_erp_strategy_do_action+0x1410/0x1938
 [<0000000000278412>] zfcp_erp_thread+0x4fa/0x1430
 [<000000000001990a>] kernel_thread_starter+0x6/0xc
 [<0000000000019904>] kernel_thread_starter+0x0/0xc

Cc: Swen Schillig <swen@vnet.ibm.com>
Cc: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>