MAINTAINERS: Add maintainer for AT24 and PCA9564/PCA9665

Add me as the maintainer for the i2c drivers I feel responsible for as I
found patches going mainline I missed due to no Cc.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>