configs: migrate CONFIG_BMP_16/24/32BPP to defconfigs

Done with:
./tools/moveconfig.py BMP_16BPP BMP_24BPP BMP_32BPP

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/riotboard_defconfig b/configs/riotboard_defconfig
index a45d541..1c632770 100644
--- a/configs/riotboard_defconfig
+++ b/configs/riotboard_defconfig
@@ -54,4 +54,5 @@
 CONFIG_SPLASH_SCREEN=y
 CONFIG_SPLASH_SCREEN_ALIGN=y
 CONFIG_VIDEO_BMP_RLE8=y
+CONFIG_BMP_16BPP=y
 CONFIG_OF_LIBFDT=y