x86/alternatives: Fixup alternative_call_2

The following pattern fails to compile while the same pattern
with alternative_call() does:

	if (...)
		alternative_call_2(...);
	else
		alternative_call_2(...);

as it expands into

	if (...)
	{
	};	<===
	else
	{
	};

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20180114120504.GA11368@avx2