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.
I'd love to meet the person who managed to use flossjtag interface
with a Stellaris board, but until we can meet, use the correct
interface, which is ti-icdi. Note that this setting is redundant,
since the board config file already specifies the correct interface;
however, OOCD_INTERFACE variable cannot be empty, by virtue of how
higher-level makefiles are written.
