[efr32] radio: increase FIFO size to allow handling of heavy traffic (#5742)
[efr32] radio: increase FIFO size to allow handling of heavy traffic (#5742)

This commit increases the FIFO size used for storing the handles of
the data request packets that were ACKed with the frame pending bit
set.
openthread/openthread,chshu/openthread,openthread/openthread,jwhui/openthread,abtink/openthread,chshu/openthread,abtink/openthread,bukepo/openthread,bukepo/openthread,srickardti/openthread,jwhui/openthread,jwhui/openthread,chshu/openthread,openthread/openthread,chshu/openthread,abtink/openthread,srickardti/openthread,bukepo/openthread,chshu/openthread,chshu/openthread,jwhui/openthread,srickardti/openthread,abtink/openthread,bukepo/openthread,srickardti/openthread,openthread/openthread