MAINTAINERS: add myself as maintainer of MCAN MMIO device driver

Since we are actively working on MMIO MCAN device driver,
as discussed with Marc, I am adding myself as a maintainer.

Signed-off-by: Sriram Dash <sriram.dash@samsung.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>