AVRCP_ext: Fix ANR issue while max connected device is 1

DeviceFeatures size equal to max conncted devices number,
while max connected device is 1, 1-deviceIndex will out
of bounds of ArrayIndex. Fix ANR issue while max connected
device is 1.

CRs-Fixed: 2266750
Change-Id: Id447707852f1554caba020cb4c88076a41657b4c
1 file changed