target/iscsi: precedence bug in iscsit_set_dataout_sequence_values()

Clang warns about this bug:
drivers/target/iscsi/iscsi_target_erl0.c:52:45: warning: operator '?:'
	has lower precedence than '+'; '+' will be evaluated first
	[-Wparentheses]

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>