gdb/csky-tdep.c: fix -Wunused-but-set-variable error

Fix these, seen when building with clang 14:

      CXX    csky-tdep.o
    /home/simark/src/binutils-gdb/gdb/csky-tdep.c:332:7: error: variable 'need_dummy_stack' set but not used [-Werror,-Wunused-but-set-variable]
      int need_dummy_stack = 0;
          ^
    /home/simark/src/binutils-gdb/gdb/csky-tdep.c:805:12: error: variable 'offset' set but not used [-Werror,-Wunused-but-set-variable]
                  int offset = 0;
                      ^

Change-Id: I6703bcb50e83c50083f716f4084ef6aa30d659c4

gdb/csky-tdep.c

@@ -329,7 +329,6 @@ csky_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
   int argnum;
   int argreg = CSKY_ABI_A0_REGNUM;
   int last_arg_regnum = CSKY_ABI_LAST_ARG_REGNUM;
-  int need_dummy_stack = 0;
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   std::vector<stack_item> stack_items;
 
@@ -399,7 +398,6 @@ csky_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
 		{
 		  /* The argument should be pushed onto the dummy stack.  */
 		  stack_items.emplace_back (4, val);
-		  need_dummy_stack += 4;
 		}
 	      len -= partial_len;
 	      val += partial_len;
@@ -802,21 +800,18 @@ csky_analyze_prologue (struct gdbarch *gdbarch,
 	  else if (CSKY_32_IS_PUSH (insn))
 	    {
 	      /* Push for 32_bit.  */
-	      int offset = 0;
 	      if (CSKY_32_IS_PUSH_R29 (insn))
 		{
 		  stacksize += 4;
 		  register_offsets[29] = stacksize;
 		  if (csky_debug)
 		    print_savedreg_msg (29, register_offsets, false);
-		  offset += 4;
 		}
 	      if (CSKY_32_PUSH_LIST2 (insn))
 		{
 		  int num = CSKY_32_PUSH_LIST2 (insn);
 		  int tmp = 0;
 		  stacksize += num * 4;
-		  offset += num * 4;
 		  if (csky_debug)
 		    {
 		      fprintf_unfiltered (gdb_stdlog,
@@ -842,14 +837,12 @@ csky_analyze_prologue (struct gdbarch *gdbarch,
 		  register_offsets[15] = stacksize;
 		  if (csky_debug)
 		    print_savedreg_msg (15, register_offsets, false);
-		  offset += 4;
 		}
 	      if (CSKY_32_PUSH_LIST1 (insn))
 		{
 		  int num = CSKY_32_PUSH_LIST1 (insn);
 		  int tmp = 0;
 		  stacksize += num * 4;
-		  offset += num * 4;
 		  if (csky_debug)
 		    {
 		      fprintf_unfiltered (gdb_stdlog,