MAINTAINERS: Add maintainer for the mmc subsystem
MAINTAINERS: Add maintainer for the mmc subsystem

Put myself as a (co)maintainer of the mmc subsystem to help out Chris
Ball in a more official role.

Signed-off-by: Ulf Hansson <fe47b31f388f85ce6ddf64bf3a0cf6b46077d0e6@linaro.org>
Signed-off-by: Chris Ball <711c73f64afdce07b7e38039a96d2224209e9a6c@printf.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs