net/ena/base: split RSS function and hash getters

net/ena/base: split RSS function and hash getters

There is no need to keep single function for both hash function and
the key. If the caller want's to get only single value, then it had to
pass NULL as one of the values, making the API harder to use.

Except reading functions from the device, one can also use function
ena_com_get_current_hash_function() to get the integer value, which
is representing current hash function stored in the ena_com layer.

Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@amazon.com>
Reviewed-by: Guy Tzalik <gtzalik@amazon.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>