common: Move conditional compilation to Makefile

common/ACEX1K.c

common/Makefile

common/altera.c

common/bedbug.c

common/cmd_onenand.c

common/cyclon2.c

common/docecc.c

common/fpga.c

common/lcd.c

common/lynxkdi.c

common/miiphybb.c

common/soft_i2c.c

common/soft_spi.c

common/spartan2.c

common/spartan3.c

common/stratixII.c

common/usb.c

common/usb_kbd.c

common/usb_storage.c

common/virtex2.c