target/jffs2: default to big endian format for big endian archs

Same logic as in target/Config.in.arch.

target/jffs2/Config.in

@@ -90,7 +90,10 @@ config BR2_TARGET_ROOTFS_JFFS2_PADSIZE
 
 choice
 	prompt "Endianess"
-	default BR2_TARGET_ROOTFS_JFFS2_LE
+	default BR2_TARGET_ROOTFS_JFFS2_BE if BR2_alpha || BR2_armeb || \
+			BR2_avr32 || BR2_m68k || BR2_mips || \
+			BR2_powerpc || BR2_sh2a_nofpueb || BR2_sh2eb || \
+			BR2_sh3eb || BR2_sh4eb || BR2_sparc || BR2_sparc64
 
 config BR2_TARGET_ROOTFS_JFFS2_LE
 	bool "little-endian"