8080586: aarch64: hotspot test compiler/codegen/7184394/TestAESMain.java fails

Return correct length in generate_cipherBlockChaining_encryptAESCrypt

Reviewed-by: roland
diff --git a/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp b/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp
index 5cf5bd7..af461db 100644
--- a/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp
+++ b/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp
@@ -1891,7 +1891,7 @@
     address start = __ pc();
       __ enter();
 
-      __ mov(rscratch1, len_reg);
+      __ mov(rscratch2, len_reg);
       __ ldrw(keylen, Address(key, arrayOopDesc::length_offset_in_bytes() - arrayOopDesc::base_offset_in_bytes(T_INT)));
 
       __ ld1(v0, __ T16B, rvec);