liquidio: fix Smatch error

Fix Smatch error by not dereferencing iq pointer if it's NULL.

See http://marc.info/?l=kernel-janitors&m=150296723301129&w=2

Also, remove unnecessary parentheses.

Fixes: d314ac22

 ("liquidio: moved liquidio_napi_poll to lio_core.c")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Intiyaz Basha <intiyaz.basha@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>