MAINTAINERS: ARM: SIRF: add the source code tree path

I got an account "baohua" from kernel.org and I'll use this tree
to maintain CSR SoCs stuff:
git://git.kernel.org/pub/scm/linux/kernel/git/baohua/linux.git

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Olof Johansson <olof@lixom.net>