firmware: calibration: split afcparams.c from rf_tables.c for gta0x

firmware: calibration: split afcparams.c from rf_tables.c for gta0x

We have new hardware targets that have appeared since the original
OS#3582 patch was created, namely Huawei GTM900-B and the upcoming
FreeCalypso Caramel2 board.  These new targets need the same APC
offset as gta0x and fcdev3b (TI's original Leonardo value), they
have proper calibration records in their FFS (meaning that all
compiled-in numbers become no-effect placeholders), and their PA
tracts are similar enough to Openmoko/FCDEV3B to where even in the
absence of calibration OM/FC numbers are close enough.  Thus most
of the tables in board/gta0x/rf_tables.c should be reusable by
these new targets.

However, these new targets have quite different VCXOs from Openmoko
and FCDEV3B, thus they need different AFC parameters.  Thus we split
board/gta0x/afcparams.c from board/gta0x/rf_tables.c, making the
latter more reusable.

Related: OS#3582
Change-Id: I92e245843253f279dd6d61bd5098766694c5215f