MIPS: Netlogic: Add XLP platform files for XLP SoC

- Update common files to support XLP.
- Add arch/mips/include/asm/netlogic/xlp-hal for register definitions
  and access macros
- Add arch/mips/netlogic/xlp/ for XLP specific files.

Signed-off-by: Jayachandran C <jayachandranc@netlogicmicro.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2967/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>