aarch64: fix typo in verify_oop_array

In aarch64 verify_oop_array, we scan over array at 'a' for 'count' oops, verifying each one.
The step for the loop should be one for each oop instead of 'size'. We may miss verifying some oops in the array if we set the step to 'size'.
Also, we should use 'temp' instead of r16 for the compressed oop case. Register r16 defined but not used in this function.

Proposed fix:

diff --git a/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp b/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp
index 89a4330137..b94e292404 100644
--- a/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp
+++ b/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp
@@ -1282,10 +1282,10 @@ class StubGenerator: public StubCodeGenerator {
       __ ldr(temp, Address(a, rscratch2, Address::lsl(exact_log2(size))));
       __ verify_oop(temp);
     } else {
- __ ldrw(r16, Address(a, rscratch2, Address::lsl(exact_log2(size))));
+ __ ldrw(temp, Address(a, rscratch2, Address::lsl(exact_log2(size))));
       __ decode_heap_oop(temp); // calls verify_oop
     }
- __ add(rscratch2, rscratch2, size);
+ __ add(rscratch2, rscratch2, 1);
     __ b(loop);
     __ bind(end);
   }