rename "swjdp_common" as "adiv5_dap"

rename "swjdp_common" as "adiv5_dap"

This partially corrects an inappropriate name choice (and its
associated FIXME).

There are still too many variables named "swjdp", bug little
current code actually relies on them referencing an SWJ-DP instead
of some other flavor of DAP.  Only the two new dap_to{swd,jtag}()
calls could behave differently on an SWJ-DP instead of a SW-DP or
a JTAG-DP.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>