liquidio: do not dereference pointer if it's NULL

Fix smatch errors by not dereferencing iq pointer if it's NULL.

See http://marc.info/?l=kernel-janitors&m=148637299004834&w=2



Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>