Add a defconfig for MIPS Creator CI20

MIPS Creator CI20 is a Linux and Android development system from
MIPS/Imagination Technologies. It incorporates an Ingenic JZ4780 SoC
which includes a 1.2GHz dual core MIPS32 processor and Imagination
PowerVR SGX540 GPU.

More information can be found at:
  http://elinux.org/MIPS_Creator_CI20



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>