Raspberry Pi: add device tree overlay support

Raspberry Pi has numerous HAT and other HW expansion options such as screens and
cameras some of which need overlays from the beginning so it makes sense to
enable evice tree overlays.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/configs/rpi_2_defconfig b/configs/rpi_2_defconfig
index f8b3ed4..be3e5e7 100644
--- a/configs/rpi_2_defconfig
+++ b/configs/rpi_2_defconfig
@@ -25,3 +25,5 @@
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_CONSOLE_SCROLL_LINES=10
 CONFIG_PHYS_TO_BUS=y
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y
diff --git a/configs/rpi_3_32b_defconfig b/configs/rpi_3_32b_defconfig
index 490af81..f0c9f49 100644
--- a/configs/rpi_3_32b_defconfig
+++ b/configs/rpi_3_32b_defconfig
@@ -27,3 +27,5 @@
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_CONSOLE_SCROLL_LINES=10
 CONFIG_PHYS_TO_BUS=y
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y
diff --git a/configs/rpi_3_defconfig b/configs/rpi_3_defconfig
index 4c0eb04..9709d53 100644
--- a/configs/rpi_3_defconfig
+++ b/configs/rpi_3_defconfig
@@ -27,3 +27,5 @@
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_CONSOLE_SCROLL_LINES=10
 CONFIG_PHYS_TO_BUS=y
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y
diff --git a/configs/rpi_defconfig b/configs/rpi_defconfig
index 1b954fe..4aa2d3e 100644
--- a/configs/rpi_defconfig
+++ b/configs/rpi_defconfig
@@ -25,3 +25,5 @@
 CONFIG_SYS_WHITE_ON_BLACK=y
 CONFIG_CONSOLE_SCROLL_LINES=10
 CONFIG_PHYS_TO_BUS=y
+CONFIG_OF_LIBFDT=y
+CONFIG_OF_LIBFDT_OVERLAY=y