x86/bugs: Expose x86_spec_ctrl_base directly

x86/bugs: Expose x86_spec_ctrl_base directly

x86_spec_ctrl_base is the system wide default value for the SPEC_CTRL MSR.
x86_spec_ctrl_get_default() returns x86_spec_ctrl_base and was intended to
prevent modification to that variable. Though the variable is read only
after init and globaly visible already.

Remove the function and export the variable instead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Orabug: 28063992
CVE: CVE-2018-3639

(cherry picked from commit fa8ac498)
Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	arch/x86/include/asm/nospec-branch.h
	arch/x86/include/asm/spec-ctrl.h
	arch/x86/kernel/cpu/bugs.c
[Contextual changes: things weren't in the expected place]

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