KVM: PPC: Book3S HV: Fix compilation with unusual configurations

This adds the "again" parameter to the dummy version of
kvmppc_check_passthru(), so that it matches the real version.
This fixes compilation with CONFIG_BOOK3S_64_HV set but
CONFIG_KVM_XICS=n.

This includes asm/smp.h in book3s_hv_builtin.c to fix compilation
with CONFIG_SMP=n.  The explicit inclusion is necessary to provide
definitions of hard_smp_processor_id() and get_hard_smp_processor_id()
in UP configs.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>