MAINTAINERS: Add a new maintainer for the CCP driver

Gary will be taking over future development of the CCP driver, so add
him as a co-maintainer of the driver.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Gary Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>