verify_file: Add constness to a few addresses.

We should not touch any data while verifying packages (or parsing the
in-memory ASN.1 structures).

Test: mmma bootable/recovery
Test: recovery_component_test passes.
Test: recovery_unit_test passes.
Change-Id: Ie990662c6451ec066a1807b3081c9296afbdb0bf
diff --git a/verifier.h b/verifier.h
index 067dab5..6bee749 100644
--- a/verifier.h
+++ b/verifier.h
@@ -65,7 +65,7 @@
  * given keys. It optionally accepts a callback function for posting the progress to. Returns one
  * of the constants of VERIFY_SUCCESS and VERIFY_FAILURE.
  */
-int verify_file(unsigned char* addr, size_t length, const std::vector<Certificate>& keys,
+int verify_file(const unsigned char* addr, size_t length, const std::vector<Certificate>& keys,
                 const std::function<void(float)>& set_progress = nullptr);
 
 bool load_keys(const char* filename, std::vector<Certificate>& certs);