net: ena: rename ena_com_free_desc to make API more uniform

Rename ena_com_free_desc to ena_com_free_q_entries to match
the LLQ mode.

In non-LLQ mode, an entry in an IO ring corresponds to a
a descriptor. In LLQ mode an entry may correspond to several
descriptors (per LLQ definition).

Signed-off-by: Igor Chauskin <igorch@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>