Remove two ReadBarrierMarkRegX entrypoints.

As entry points ReadBarrierMarkReg30 and
ReadBarrierMarkReg31 are undefined on all architectures
supporting the read barrier configuration (ARM, ARM64, x86
and x86-64), remove them from the entry point list.

Test: ART host and target (ARM, ARM64) tests.
Bug: 29506760
Bug: 12687968
Change-Id: I500626e54f00aebfc095b4ef5f81b49fa43f7768
diff --git a/runtime/entrypoints_order_test.cc b/runtime/entrypoints_order_test.cc
index ffe4109..e3203dc 100644
--- a/runtime/entrypoints_order_test.cc
+++ b/runtime/entrypoints_order_test.cc
@@ -383,11 +383,7 @@
                          sizeof(void*));
     EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierMarkReg28, pReadBarrierMarkReg29,
                          sizeof(void*));
-    EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierMarkReg29, pReadBarrierMarkReg30,
-                         sizeof(void*));
-    EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierMarkReg30, pReadBarrierMarkReg31,
-                         sizeof(void*));
-    EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierMarkReg31, pReadBarrierSlow, sizeof(void*));
+    EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierMarkReg29, pReadBarrierSlow, sizeof(void*));
     EXPECT_OFFSET_DIFFNP(QuickEntryPoints, pReadBarrierSlow, pReadBarrierForRootSlow,
                          sizeof(void*));