zram-swap: correctly express the required dependencies

The block-mount swapon implementation doesn't support discard, so make zram-swap
depend only on the default BusyBox implementation or, when unavailable, on the
one present in the swap-utils package.

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>

package/system/zram-swap/Makefile

@@ -18,7 +18,7 @@ include $(INCLUDE_DIR)/package.mk
 define Package/zram-swap
   SECTION:=utils
   CATEGORY:=Base system
-  DEPENDS:=+kmod-zram +!(BUSYBOX_DEFAULT_MKSWAP||BUSYBOX_CONFIG_MKSWAP):swap-utils +!((BUSYBOX_DEFAULT_SWAPON||BUSYBOX_CONFIG_SWAPON)&&(BUSYBOX_DEFAULT_SWAPOFF||BUSYBOX_CONFIG_SWAPOFF)):block-mount
+  DEPENDS:=+kmod-zram +!(BUSYBOX_CONFIG_MKSWAP&&BUSYBOX_CONFIG_SWAPON&&BUSYBOX_CONFIG_SWAPOFF):swap-utils
   TITLE:=ZRAM swap scripts
   PKGARCH:=all
 endef