x86: prevent C-states hang on AMD C1E enabled machines

Impact: System hang when AMD C1E machines switch into C2/C3

AMD C1E enabled systems do not work with normal ACPI C-states 
even if the BIOS is advertising them. Limit the C-states to 
C1 for the ACPI processor idle code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/process.c

@@ -272,6 +272,7 @@ static void c1e_idle(void)
 			c1e_detected = 1;
 			mark_tsc_unstable("TSC halt in C1E");
 			printk(KERN_INFO "System has C1E enabled\n");
+			set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
 		}
 	}