Direction finding functionality does antenna switching during CTE
reception in AoA mode and CTE transmission in AoD mode. Antennas are
switched according to user provided antenna switch pattern. If a CTE
length is enough to exhaust all antenna ids in a switch pattern then
Radio should loopback to reference antenna and continue from switching
from it.
Current implementation loops back to wrong antenna due to wrong index
used in GUARD_REF_ANTENNA_PATTERN_IDX. It was set to one instead of
zero. Zero is the index of reference antenna in Host provided antenna
switching pattern array.
Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>