net: ena: fix broken interface between ENA driver and FW

In this commit we revert the part of
commit 1a63443a ("net/amazon: Ensure that driver version is aligned to the linux kernel"),
which breaks the interface between the ENA driver and FW.

We also replace the use of DRIVER_VERSION with DRIVER_GENERATION
when we bring back the deleted constants that are used in interface with
ENA device FW.

This commit does not change the driver version reported to the user via
ethtool, which remains the kernel version.

Fixes: 1a63443a

 ("net/amazon: Ensure that driver version is aligned to the linux kernel")
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>