MAINTAINERS: Remove T Ambarus from few mchp entries

I have been no longer at Microchip for more than a year and I'm no
longer interested in maintaining these drivers. Let other mchp people
step up, thus remove myself. Thanks for the nice collaboration everyone!

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>