x86/speculation: Create spec-ctrl.h to avoid include hell

x86/speculation: Create spec-ctrl.h to avoid include hell

Having everything in nospec-branch.h creates a hell of dependencies when
adding the prctl based switching mechanism. Move everything which is not
required in nospec-branch.h to spec-ctrl.h and fix up the includes in the
relevant files.

OraBug: 28041771
CVE: CVE-2018-3639

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 28a2775217b17208811fa43a9e96bd1fdf417b86)
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Mihai Carabas <mihai.carabas@oracle.com>
 Conflicts:
	arch/x86/kernel/cpu/bugs.c
	arch/x86/kvm/svm.c
	arch/x86/kvm/vmx.c

Signed-off-by: Brian Maly <brian.maly@oracle.com>