profiling: Properly align register_data.

Move ArchEnum to last member to improve struct packing.

Change-Id: Iefd0188230d43b32cb3e4043c90f997f321d16d8
diff --git a/src/profiling/memory/wire_protocol.h b/src/profiling/memory/wire_protocol.h
index e2c5f80..a3b2212 100644
--- a/src/profiling/memory/wire_protocol.h
+++ b/src/profiling/memory/wire_protocol.h
@@ -68,10 +68,10 @@
   uint64_t stack_pointer;
   // Offset of the data at stack_pointer from the start of this record.
   uint64_t stack_pointer_offset;
+  alignas(uint64_t) char register_data[kMaxRegisterDataSize];
   // CPU architecture of the client. This determines the size of the
   // register data that follows this struct.
   unwindstack::ArchEnum arch;
-  char register_data[kMaxRegisterDataSize];
 };
 
 struct FreePageEntry {