serial-lcr: also request packets before initial state retrieval

serial-lcr: also request packets before initial state retrieval

Commit cb5cd1538f5d introduced packet request support in the serial-lcr
device driver. Calls were added to the detection of the device's
presence, and the periodic acquisition of measurement data. Add another
call to the device configuration retrieval that follows the presence
detection, without it communication timed out with no data received.

Also slightly raise the timeout for this device configuration gathering
phase. With one second sharp, the VC4080 was detected, but getting its
current configuration kept failing. This device's serial communication
is extra slow (1200 bps) and the packets are rather large (39 bytes).
Which made the stream detect's receive routine stop checking for the
availability of more data while a packet was being received.