[SCSI] iscsi: fix 64 bit compile warning

drivers/scsi/scsi_transport_iscsi.c: In function `show_transport_handle':
drivers/scsi/scsi_transport_iscsi.c:100: warning: long long unsigned int format, long unsigned int arg (arg 3)

is caused because uint64_t is only unsigned long on a 64 bit platform.
Fix this by casting to unsigned long long.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>