MAINTAINERS: update email addresses of octeon_ep driver maintainers

Update email addresses of Marvell octeon_ep driver maintainers.
Also remove a former maintainer.

As a maintainer below are the responsibilities:
- Pushing the bug fixes and new features to upstream.
- Responsible for reviewing the external changes
  submitted for the octeon_ep driver.
- Reply to maintainers questions in a timely manner.

Signed-off-by: Sathesh Edara <sedara@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>