[SCSI] gdth: fix oops in gdth_copy_cmd()

Recent alterations to the gdth_fill_raw_cmd() path no longer set the
sg_ranz field for zero transfer commands. However, this field is used
lower down in the function to initialise ha->cmd_len to the size of
the firmware packet.  If this uninitialised field contains a bogus
value, ha->cmd_len can become much larger than the actual firmware
packet and end up oopsing in gdth_copy_cmd() as it tries to copy this
huge packet to the device (usually because it runs into an unallocated
page).

The fix is to initialise the sg_ranz field to zero at the start of
gdth_fill_raw_cmd().

Signed-off-by: Joerg Dorchain <joerg@dorchain.net>
Acked-by: "Leubner, Achim" <Achim_Leubner@adaptec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>