Ubuntu: [Config]: enable Speculative Return Stack Overflow mitigation

CVE-2023-20569

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

debian.master/config/annotations

@@ -3125,6 +3125,7 @@ CONFIG_CPU_PJ4B                                 policy<{'armhf': 'y'}>
 CONFIG_CPU_PM                                   policy<{'arm64': 'y', 'armhf': 'y', 'riscv64': 'y'}>
 CONFIG_CPU_RMAP                                 policy<{'amd64': 'y', 'arm64': 'y', 'armhf': 'y', 'ppc64el': 'y', 'riscv64': 'y', 's390x': 'y'}>
 CONFIG_CPU_SPECTRE                              policy<{'armhf': 'y'}>
+CONFIG_CPU_SRSO                                 policy<{'amd64': 'y'}>
 CONFIG_CPU_SUP_AMD                              policy<{'amd64': 'y'}>
 CONFIG_CPU_SUP_CENTAUR                          policy<{'amd64': 'y'}>
 CONFIG_CPU_SUP_HYGON                            policy<{'amd64': 'y'}>