Revert "x86/idle: Disable IBRS when offlining cpu and re-enable on wakeup"

CVE-2017-5753 (revert embargoed)
CVE-2017-5715 (revert embargoed)

This reverts commit 92e0b0d6.
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/kernel/smpboot.c

@@ -75,7 +75,6 @@
 #include <asm/i8259.h>
 #include <asm/realmode.h>
 #include <asm/misc.h>
-#include <asm/microcode.h>
 
 /* Number of siblings per CPU package */
 int smp_num_siblings = 1;
@@ -1657,15 +1656,9 @@ void native_play_dead(void)
 	play_dead_common();
 	tboot_shutdown(TB_SHUTDOWN_WFS);
 
-	if (boot_cpu_has(X86_FEATURE_SPEC_CTRL))
-		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
-
 	mwait_play_dead();	/* Only returns on failure */
 	if (cpuidle_play_dead())
 		hlt_play_dead();
-
-	if (boot_cpu_has(X86_FEATURE_SPEC_CTRL))
-		native_wrmsrl(MSR_IA32_SPEC_CTRL, FEATURE_ENABLE_IBRS);
 }
 
 #else /* ... !CONFIG_HOTPLUG_CPU */