scsi: dpt_i2o: Remove VLA usage

On the quest to remove all VLAs from the kernel[1] this moves the
sg_list variable off the stack, as already done for other allocated
buffers in adpt_i2o_passthru(). Additionally consolidates the error path
for kfree().

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com



Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>