gdbstub: Prefer cached CpuClass over CPU_GET_CLASS() macro

CpuState caches its CPUClass since commit 6fbdff87062
("cpu: cache CPUClass in CPUState for hot code paths"),
use it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250122093028.52416-9-philmd@linaro.org>
diff --git a/gdbstub/user.c b/gdbstub/user.c
index 3730f32..67403e5 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -743,11 +743,8 @@
 int gdb_target_memory_rw_debug(CPUState *cpu, hwaddr addr,
                                uint8_t *buf, int len, bool is_write)
 {
-    CPUClass *cc;
-
-    cc = CPU_GET_CLASS(cpu);
-    if (cc->memory_rw_debug) {
-        return cc->memory_rw_debug(cpu, addr, buf, len, is_write);
+    if (cpu->cc->memory_rw_debug) {
+        return cpu->cc->memory_rw_debug(cpu, addr, buf, len, is_write);
     }
     return cpu_memory_rw_debug(cpu, addr, buf, len, is_write);
 }