targets/fcdev3b.h: bring back CONFIG_TARGET_FCDEV3B C preprocessor symbol CONFIG_TARGET_FCMODEM is no longer used anywhere in our code base, thus it is being fully retired. OTOH, CONFIG_TARGET_FCDEV3B is being brought back: with our earlier FC modem family idea now being withdrawn in light of the discovery of Tango modules, FCDEV3B goes back to being its own unique target.

#define	CONFIG_TARGET_DSAMPLE	1
#define	GPIO1_SPEAKER_CTRL	1
#define	UARTFAX_CLASSIC_DTR_DCD	1
#define	TARGET_HAS_LPG		1
#define	TARGET_HAS_PWL		1