retpoline: set IBRS and IBPB in use only on the boot CPU call to init_scattered_cpuid...

retpoline: set IBRS and IBPB in use only on the boot CPU call to init_scattered_cpuid_features()

Setting IBRS and IBPB in use is a system wide issue, not a per-CPU
issue.  Set them only on the boot CPU's call to
init_scattered_cpuid_features().

Orabug: 27625404
Signed-off-by: Chuck Anderson <chuck.anderson@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Conflicts:
	arch/x86/kernel/cpu/scattered.c
	(merged with be596ab27 ("x86/speculation: Use IBRS if available before
	 calling into firmware"))