kernel: add kmod-lib-zstd

In kernel 4.14 kmod-fs-btrfs depends on the zstd compression libraries,
add it to the package system.

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

package/kernel/linux/modules/fs.mk

@@ -82,7 +82,7 @@ $(eval $(call KernelPackage,fs-autofs4))
 define KernelPackage/fs-btrfs
   SUBMENU:=$(FS_MENU)
   TITLE:=BTRFS filesystem support
-  DEPENDS:=+kmod-lib-crc32c +kmod-lib-lzo +kmod-lib-zlib-inflate +kmod-lib-zlib-deflate +kmod-lib-raid6 +kmod-lib-xor
+  DEPENDS:=+kmod-lib-crc32c +kmod-lib-lzo +kmod-lib-zlib-inflate +kmod-lib-zlib-deflate +kmod-lib-raid6 +kmod-lib-xor +LINUX_4_14:kmod-lib-zstd
   KCONFIG:=\
 	CONFIG_BTRFS_FS \
 	CONFIG_BTRFS_FS_POSIX_ACL=n \

package/kernel/linux/modules/lib.mk

@@ -120,6 +120,28 @@ endef
 $(eval $(call KernelPackage,lib-lzo))
 
 
+define KernelPackage/lib-zstd
+  SUBMENU:=$(LIB_MENU)
+  TITLE:=ZSTD support
+  KCONFIG:= \
+	CONFIG_ZSTD_COMPRESS \
+	CONFIG_ZSTD_DECOMPRESS \
+	CONFIG_XXHASH
+  HIDDEN:=1
+  FILES:= \
+	$(LINUX_DIR)/lib/xxhash.ko \
+	$(LINUX_DIR)/lib/zstd/zstd_compress.ko \
+	$(LINUX_DIR)/lib/zstd/zstd_decompress.ko
+  AUTOLOAD:=$(call AutoProbe,xxhash zstd_compress zstd_decompress)
+endef
+
+define KernelPackage/lib-zstd/description
+ Kernel module for ZSTD compression/decompression support
+endef
+
+$(eval $(call KernelPackage,lib-zstd))
+
+
 define KernelPackage/lib-lz4
   SUBMENU:=$(LIB_MENU)
   TITLE:=LZ4 support