MIPS: Add default configuration for XLR/XLS processors

Enable XLR CPU support, SMP, initramfs based root filesystem etc.

[ralf@linux-mips.org: shrink the defconfig file through make savedefconfig.]
Signed-off-by: Jayachandran C <jayachandranc@netlogicmicro.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2338/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>