MAINTAINERS: Add Silvaco I3C master

Add Conor and myself as maintainers.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210121101808.14654-7-miquel.raynal@bootlin.com