kernel: kmod-zram: deactivate CONFIG_ZRAM_WRITEBACK for kernel 4.14

This new option was introduced in kernel 4.14 and should be deactivated
by default.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/kernel/linux/modules/other.mk

@@ -693,6 +693,7 @@ define KernelPackage/zram
 	CONFIG_ZRAM \
 	CONFIG_ZRAM_DEBUG=n \
 	CONFIG_PGTABLE_MAPPING=n \
+	CONFIG_ZRAM_WRITEBACK=n \
 	CONFIG_ZSMALLOC_STAT=n \
 	CONFIG_ZRAM_LZ4_COMPRESS=y
   FILES:= \