net: ena: Change RSS related macros and variables names

The formal name changes to "ENA_ADMIN_RSS_INDIRECTION_TABLE_CONFIG".
Indirection is the ability to reference "something" using "something else"
instead of the value itself.
Indirection table, as the name implies, is the ability to reference
CPU/Queue value using hash-to-CPU table instead of CPU/Queue itself.

This patch renames the variable keys_num, which describes the number of
words in the RSS hash key, to key_parts which makes its purpose clearer
in RSS context.

Signed-off-by: Amit Bernstein <amitbern@amazon.com>
Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>