8248671: AArch64: Remove unused variables

Remove unused variables in the AArch64 backend. Detected by compiling with MSVC, which warns about them.

Co-authored-by: Bernhard Urban-Forster <burban@openjdk.org>
Backport-of: dff37f8

src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp

@@ -2314,7 +2314,6 @@ void LIR_Assembler::emit_arraycopy(LIR_OpArrayCopy* op) {
   assert(default_type != NULL && default_type->is_array_klass() && default_type->is_loaded(), "must be true at this point");
 
   int elem_size = type2aelembytes(basic_type);
-  int shift_amount;
   int scale = exact_log2(elem_size);
 
   Address src_length_addr = Address(src, arrayOopDesc::length_offset_in_bytes());

src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp

@@ -683,7 +683,6 @@ class StubGenerator: public StubCodeGenerator {
     int unit = wordSize * direction;
     int bias = (UseSIMDForMemoryOps ? 4:2) * wordSize;
 
-    int offset;
     const Register t0 = r3, t1 = r4, t2 = r5, t3 = r6,
       t4 = r7, t5 = r10, t6 = r11, t7 = r12;
     const Register stride = r13;