target/arm/gdbstub: Only advertise M-profile features if TCG available

Cortex-M profile is only emulable from TCG accelerator. Restrict
the GDBstub features to its availability in order to avoid a link
error when TCG is not enabled:

  Undefined symbols for architecture arm64:
    "_arm_v7m_get_sp_ptr", referenced from:
        _m_sysreg_get in target_arm_gdbstub.c.o
    "_arm_v7m_mrs_control", referenced from:
        _arm_gdb_get_m_systemreg in target_arm_gdbstub.c.o
  ld: symbol(s) not found for architecture arm64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)

Fixes: 7d8b28b8b5 ("target/arm: Implement gdbstub m-profile systemreg and secext")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20230322142902.69511-3-philmd@linaro.org
[PMM: add #include since I cherry-picked this patch from the series]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/gdbstub.c

@@ -21,6 +21,7 @@
 #include "cpu.h"
 #include "exec/gdbstub.h"
 #include "gdbstub/helpers.h"
+#include "sysemu/tcg.h"
 #include "internals.h"
 #include "cpregs.h"
 
@@ -553,7 +554,7 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
                                      2, "arm-vfp-sysregs.xml", 0);
         }
     }
-    if (cpu_isar_feature(aa32_mve, cpu)) {
+    if (cpu_isar_feature(aa32_mve, cpu) && tcg_enabled()) {
         gdb_register_coprocessor(cs, mve_gdb_get_reg, mve_gdb_set_reg,
                                  1, "arm-m-profile-mve.xml", 0);
     }
@@ -561,7 +562,7 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
                              arm_gen_dynamic_sysreg_xml(cs, cs->gdb_num_regs),
                              "system-registers.xml", 0);
 
-    if (arm_feature(env, ARM_FEATURE_M)) {
+    if (arm_feature(env, ARM_FEATURE_M) && tcg_enabled()) {
         gdb_register_coprocessor(cs,
             arm_gdb_get_m_systemreg, arm_gdb_set_m_systemreg,
             arm_gen_dynamic_m_systemreg_xml(cs, cs->gdb_num_regs),