Add missing header <asm/smp.h> on include/asm/smp_plat.h, as it calls function
cpu_logical_map(). Also include it on kernel/cpufeature.c since it has calls to
functions cpu_panic_kernel() and cpu_die_early().

Both files call functions defined on this header, make the header dependencies
less fragile.
Signed-off-by: Carlos Bilbao <bilbao@vt.edu>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/4325940.LvFx2qVVIh@iron-maidenSigned-off-by: Will Deacon <will@kernel.org>