x86/bugs: Add retbleed=force

Debug aid, allows running retbleed=force,stuff on non-affected uarchs
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

arch/x86/kernel/cpu/bugs.c

@@ -838,6 +838,8 @@ static int __init retbleed_parse_cmdline(char *str)
 			retbleed_cmd = RETBLEED_CMD_STUFF;
 		} else if (!strcmp(str, "nosmt")) {
 			retbleed_nosmt = true;
+		} else if (!strcmp(str, "force")) {
+			setup_force_cpu_bug(X86_BUG_RETBLEED);
 		} else {
 			pr_err("Ignoring unknown retbleed option (%s).", str);
 		}