efi_loader: signature: export efi_hash_regions()

This function is used to calculate a message digest as part of
authentication process in a later patch.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
index ddac751..742d891 100644
--- a/lib/efi_loader/efi_signature.c
+++ b/lib/efi_loader/efi_signature.c
@@ -125,8 +125,8 @@
  *
  * Return:	true on success, false on error
  */
-static bool efi_hash_regions(struct image_region *regs, int count,
-			     void **hash, const char *hash_algo, int *len)
+bool efi_hash_regions(struct image_region *regs, int count,
+		      void **hash, const char *hash_algo, int *len)
 {
 	int ret, hash_len;