kernel|lib: change driver name and device name

The name 'ft' is not meaningful for everyone

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
kernel: coalescing 40 tstamp/40ms

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
kernel: clear IRQ

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
kernel: use IRQ_NONE instead of '0'

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
kernel: add WR calibration offset
kernel: apply WR timebase offset on readout
style: checkpatch fixes

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>