MIPS: pic32mzdask: switch to CONFIG_OF_SEPARATE

Fix the Kconfig warning to not use CONFIG_OF_EMBED in defconfigs.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/configs/pic32mzdask_defconfig b/configs/pic32mzdask_defconfig
index de699fc..d411031 100644
--- a/configs/pic32mzdask_defconfig
+++ b/configs/pic32mzdask_defconfig
@@ -21,7 +21,6 @@
 CONFIG_CMD_EXT4_WRITE=y
 # CONFIG_ISO_PARTITION is not set
 # CONFIG_EFI_PARTITION is not set
-CONFIG_OF_EMBED=y
 CONFIG_DEFAULT_DEVICE_TREE="pic32mzda_sk"
 CONFIG_NET_RANDOM_ETHADDR=y
 # CONFIG_BLK is not set