shared/hfp: Fix calling io read function directly
shared/hfp: Fix calling io read function directly

can_read_data function should by called only from IO read callback.
can_read_data feeds ringbuffer but don't call process_input() if
there is pending result. So it is enought to just call process_input
cause any pending data are already present in ring_buffer.

This fix blocking read in unit/test-hfp exposed by previous patch.

silent-snowman/bluez,silent-snowman/bluez,ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pkarasev3/bluez,pkarasev3/bluez,silent-snowman/bluez,pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez