afsplitter: Move into its own module

While the AFSplitter code is currently used only by the luks module,
upcoming support for luks2 will add a second module that depends on it.
To avoid any linker errors when adding the code to both modules because
of duplicated symbols, this commit moves it into its own standalone
module afsplitter as a preparatory step.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/Makefile.core.def

@@ -1181,10 +1181,14 @@ module = {
   common = lib/json/json.c;
 };
 
+module = {
+  name = afsplitter;
+  common = disk/AFSplitter.c;
+};
+
 module = {
   name = luks;
   common = disk/luks.c;
-  common = disk/AFSplitter.c;
 };
 
 module = {

grub-core/disk/AFSplitter.c

@@ -21,9 +21,12 @@
  */
 
 #include <grub/crypto.h>
+#include <grub/dl.h>
 #include <grub/mm.h>
 #include <grub/misc.h>
 
+GRUB_MOD_LICENSE ("GPLv2+");
+
 gcry_err_code_t AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src,
 			  grub_uint8_t * dst, grub_size_t blocksize,
 			  grub_size_t blocknumbers);