image: don't force ubifs journal size

Small journal size can lead to problems if nand flash is too big. By default
ubifs will use ~12% of volume size or a maximum of 8MiB.

Signed-off-by: Luka Perkov <luka@openwrt.org>

SVN-Revision: 38799

Config.in

@@ -143,7 +143,7 @@ menu "Target Images"
 		config TARGET_UBIFS_JOURNAL_SIZE
 			string
 			prompt "journal size" if TARGET_ROOTFS_UBIFS
-			default "512KiB"
+			default ""
 
 		config TARGET_UBIFS_SQUASH_UIDS
 			bool "squash uids" if TARGET_ROOTFS_UBIFS

include/image.mk

@@ -142,7 +142,7 @@ ifneq ($(CONFIG_TARGET_ROOTFS_UBIFS),)
 			$(if $(CONFIG_TARGET_UBIFS_COMPRESSION_NONE),--force-compr=none) \
 			$(if $(CONFIG_TARGET_UBIFS_COMPRESSION_LZO),--force-compr=lzo) \
 			$(if $(CONFIG_TARGET_UBIFS_COMPRESSION_ZLIB),--force-compr=zlib) \
-			--jrn-size=$(CONFIG_TARGET_UBIFS_JOURNAL_SIZE) \
+			$(if $(shell echo $(CONFIG_TARGET_UBIFS_JOURNAL_SIZE)),--jrn-size=$(CONFIG_TARGET_UBIFS_JOURNAL_SIZE)) \
 			--squash-uids \
 			-o $(KDIR)/root.ubifs \
 			-d $(TARGET_DIR)