liquidio: remove set but not used variable 'irh'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/cavium/liquidio/request_manager.c: In function 'lio_process_iq_request_list':
drivers/net/ethernet/cavium/liquidio/request_manager.c:383:27: warning:
 variable 'irh' set but not used [-Wunused-but-set-variable]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>