ART: Change return types of field access entrypoints

Ensure that return types guarantee full-width data as the compiled
code and mterp expect by using size_t and ssize_t.

This fixes Clang no longer sign-/zero-extending small return types.

Bug: 30232671
Test: m ART_TEST_RUN_TEST_NDEBUG=true ART_TEST_INTERPRETER=true test-art-host-run-test
Change-Id: Ic505befc6c94e2dccbc8abf2b13d4c2d662e68d1
diff --git a/runtime/arch/arm/entrypoints_init_arm.cc b/runtime/arch/arm/entrypoints_init_arm.cc
index 8f18ff3..e48a164 100644
--- a/runtime/arch/arm/entrypoints_init_arm.cc
+++ b/runtime/arch/arm/entrypoints_init_arm.cc
@@ -27,8 +27,8 @@
 namespace art {
 
 // Cast entrypoints.
-extern "C" uint32_t artIsAssignableFromCode(const mirror::Class* klass,
-                                            const mirror::Class* ref_class);
+extern "C" size_t artIsAssignableFromCode(const mirror::Class* klass,
+                                          const mirror::Class* ref_class);
 
 // Read barrier entrypoints.
 // art_quick_read_barrier_mark_regX uses an non-standard calling