MAINTAINERS: Add an entry for the Maxim MAX77802 PMIC drivers

I added support for the max77802 drivers and have been maintaining them.
So add an entry for these drivers to make tools like get_maintainer.pl
to work and make people submitting patches add me to the CC list.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>