MIPS: Netlogic: Split XLP device tree code to dt.c

Create new flle arch/mips/netlogic/xlp/dt.c and move the device
tree related code there.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5422/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>