net: ena: store values in their appropriate variables types

This patch changes some of the variables types to match the values they
hold. These wrong types fail some of our static checkers that search for
accidental conversions in our driver.

Signed-off-by: Ido Segev <idose@amazon.com>
Signed-off-by: Igor Chauskin <igorch@amazon.com>
Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>