Add myself as a maintainer

I will be overseeing the code in this repository.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I719b4f1db756e11797f45c951a2c18bb52017407

Add MAINTAINERS file

Change-Id: Id5a42b4fcff06c7b52cb6e219876b78190555e15
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>