MIPS: add initial infrastructure for device-tree files

Prepare sub-folder for device-tree files. Make support for
device-tree on MIPS available in Kbuild/Kconfig.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
diff --git a/arch/mips/dts/.gitignore b/arch/mips/dts/.gitignore
new file mode 100644
index 0000000..b60ed20
--- /dev/null
+++ b/arch/mips/dts/.gitignore
@@ -0,0 +1 @@
+*.dtb