At the end the carrier offset value for White-Rabbit has been always
constant and it depends on the hardware:
- SVEC: 3000 ps
- SPEC:    0 ps

so, instead of complicate users life by setting this module parameter,
here I am embedding it into the platform_data for the TDC.

The ideal solution would be to ignore this value in software and to
apply it in HDL directly.
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>