kernel: modules: fs: add missing backslash

Commit 7db0748b7b ("kernel: modules: split package fs-fscache") modified
the KCONFIG section of KernelPackage/fs-netfs but missed to add a
backslash to escape a linebreak. Add it now.

Fixes: 7db0748b7b ("kernel: modules: split package fs-fscache")
Signed-off-by: Daniel Golle <[email protected]>

package/kernel/linux/modules/fs.mk

@@ -429,7 +429,7 @@ $(eval $(call KernelPackage,fs-msdos))
 define KernelPackage/fs-netfs
   SUBMENU:=$(FS_MENU)
   TITLE:=Network Filesystems support
-  KCONFIG:=
+  KCONFIG:= \
 	CONFIG_NETFS_SUPPORT \
 	[email protected] \
 	[email protected]