lib/ukvmem: Add dependency on CONFIG_PAGING

Since you cannot use `ukvmem` without the paging API's, it makes
sense to add a dependency on the `CONFIG_PAGING` configuration entry.

Signed-off-by: Sergiu Moga <sergiu.moga@protonmail.com>

lib/ukvmem/Config.uk

@@ -4,6 +4,7 @@ menuconfig LIBUKVMEM
 	select LIBUKDEBUG
 	select LIBUKALLOC
 	select LIBISRLIB
+	select PAGING
 	help
 		This library implements virtual address management by
 		providing methods for working with virtual address space