MAINTAINERS: change ENA driver maintainers email domain

ENA driver was developed by developers from Annapurna Labs.
Annapurna Labs was acquired by Amazon and the company's domain
(@annapurnalabs.com) will become deprecated soon.

Update the email addresses of the maintainers to the alternative amazon
emails (@amazon.com)

Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>