ionic: Prevent filter add/del err msgs when the device is not available

Currently when a request for add/deleting a filter is made when
ionic_heartbeat_check() returns failure the driver will be overly
verbose about failures, especially when these are usually temporary
fails and the request will be retried later. An example of this is
a filter add when the FW is in the middle of resetting:

IONIC_CMD_RX_FILTER_ADD (31) failed: IONIC_RC_ERROR (-6)
rx_filter add failed: ADDR 01:80:c2:00:00:0e

Fix this by checking for -ENXIO and other error values on filter
request fails before printing the error message.  Add similar
checking to the delete filter code.

Fixes: f91958cc ("ionic: tame the filter no space message")
Signed-off-by: Brett Creeley <brett@pensando.io>
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>