soc: x86: apollo_lake: Fix default timer selection

The APIC timer is not supported e.g. with SMP (which will be enabled
by default soon as well) so the sensible choice is to default to HPET.
Also, the default makes more sense to be on the SoC side, so move it
there from the board defaults.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>