Revert "x86/enter: MACROS to set/clear IBRS and set IBPB"

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

This reverts commit f011884a.
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/include/asm/spec_ctrl.h

-#ifndef _ASM_X86_SPEC_CTRL_H
-#define _ASM_X86_SPEC_CTRL_H
-
-#include <linux/stringify.h>
-#include <asm/msr-index.h>
-#include <asm/cpufeatures.h>
-#include <asm/alternative-asm.h>
-
-#ifdef __ASSEMBLY__
-
-#define __ASM_ENABLE_IBRS			\
-	pushq %rax;				\
-	pushq %rcx;				\
-	pushq %rdx;				\
-	movl $MSR_IA32_SPEC_CTRL, %ecx;		\
-	movl $0, %edx;				\
-	movl $FEATURE_ENABLE_IBRS, %eax;	\
-	wrmsr;					\
-	popq %rdx;				\
-	popq %rcx;				\
-	popq %rax
-#define __ASM_ENABLE_IBRS_CLOBBER		\
-	movl $MSR_IA32_SPEC_CTRL, %ecx;		\
-	movl $0, %edx;				\
-	movl $FEATURE_ENABLE_IBRS, %eax;	\
-	wrmsr;
-#define __ASM_DISABLE_IBRS			\
-	pushq %rax;				\
-	pushq %rcx;				\
-	pushq %rdx;				\
-	movl $MSR_IA32_SPEC_CTRL, %ecx;		\
-	movl $0, %edx;				\
-	movl $0, %eax;				\
-	wrmsr;					\
-	popq %rdx;				\
-	popq %rcx;				\
-	popq %rax
-
-.macro ENABLE_IBRS
-ALTERNATIVE "", __stringify(__ASM_ENABLE_IBRS), X86_FEATURE_SPEC_CTRL
-.endm
-
-.macro ENABLE_IBRS_CLOBBER
-ALTERNATIVE "", __stringify(__ASM_ENABLE_IBRS_CLOBBER), X86_FEATURE_SPEC_CTRL
-.endm
-
-.macro DISABLE_IBRS
-ALTERNATIVE "", __stringify(__ASM_DISABLE_IBRS), X86_FEATURE_SPEC_CTRL
-.endm
-
-#endif /* __ASSEMBLY__ */
-#endif /* _ASM_X86_SPEC_CTRL_H */