MAINTAINERS: Add Revanth Rajashekar as a SED-Opal maintainer

Scott hasn't worked for Intel for some time and has already given us his
blessing.

CC: Scott Bauer <sbauer@plzdonthack.me>
Signed-off-by: Revanth Rajashekar <revanth.rajashekar@intel.com>
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>