net: liquidio: Add missing null pointer checks

The functions send_rx_ctrl_cmd() in both liquidio/lio_main.c and
liquidio/lio_vf_main.c do not check if the call to
octeon_alloc_soft_command() fails and returns a null pointer. Both
functions also return void so errors are not propagated back to the
caller.

Fix these issues by updating both instances of send_rx_ctrl_cmd() to
return an integer rather than void, and have them return -ENOMEM if an
allocation failure occurs. Also update all callers of send_rx_ctrl_cmd()
so that they now check the return value.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Tom Seewald <tseewald@gmail.com>
Link: https://lore.kernel.org/r/20210503115736.2104747-66-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>