rx: switch boards to "default y"

Some targets use "default y" for boards to filter out those that require
TCG.  For consistency we are switching all other targets to do the same.
Continue with RX.

No changes to generated config-devices.mak file.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/.gitlab-ci.d/buildtest.yml b/.gitlab-ci.d/buildtest.yml
index a65b5fc..13f505f 100644
--- a/.gitlab-ci.d/buildtest.yml
+++ b/.gitlab-ci.d/buildtest.yml
@@ -649,7 +649,7 @@
 
 # Check our reduced build configurations
 # requires libfdt: aarch64, arm, i386, loongarch64, microblaze, microblazeel,
-#   mips64el, or1k, ppc, ppc64, riscv32, riscv64, x86_64
+#   mips64el, or1k, ppc, ppc64, riscv32, riscv64, rx, x86_64
 # does not build without boards: i386, loongarch64, x86_64
 build-without-defaults:
   extends: .native_build_job_template
diff --git a/configs/devices/rx-softmmu/default.mak b/configs/devices/rx-softmmu/default.mak
index df2b4e4..e7caebe 100644
--- a/configs/devices/rx-softmmu/default.mak
+++ b/configs/devices/rx-softmmu/default.mak
@@ -1,3 +1,4 @@
 # Default configuration for rx-softmmu
 
-CONFIG_RX_GDBSIM=y
+# Boards are selected by default, uncomment to keep out of the build.
+# CONFIG_RX_GDBSIM=n
diff --git a/hw/rx/Kconfig b/hw/rx/Kconfig
index 2b297c5..b2fa2b7 100644
--- a/hw/rx/Kconfig
+++ b/hw/rx/Kconfig
@@ -7,4 +7,6 @@
 
 config RX_GDBSIM
     bool
+    default y
+    depends on RX
     select RX62N_MCU