Some demos will use object files from a different directory and
those files would not be cleaned by the simple CLEAN rule. This
small change insures that those objects and their dependency files
are also cleaned.
Instead of OOCD_SERIAL triggering an attempt to use a specific ftdi based
adapter, introduce common target/interface pairs, OOCD_INTERFACE and
OOCD_TARGET, and an override via OOCD_FILE allowing full control.
Further, attempt to connect to a running openocd instance to flash if possible.
This _will not_ work well if you have multiple openocd instances open at once,
but that's a rare use case.
Examples:
OOCD_INTERFACE=stlink-v2
OOCD_TARGET=stm32f0x
--> openocd ... -f interface/stlink-v2.cfg -f target/stm32f0x.cfg)
OOCD_FILE=board/ek-lm4f120xl.cfg
--> openocd ... -f $(OOCD_FILE) (ie, the variable is passed untouched)
As part of implementing this, correct variables that were always wrong, and
update the openocd flashing commands to use current commands.
