net: ena: fix ena_com_comp_status_to_errno() return value

Default return value should be -EINVAL since the input
in this case was unexpected.
Also remove the now redundant check in the beginning
of the function.

Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>