jtag: rewrite commands 'jtag newtap' and 'swd newdap' as COMMAND_HANDLER

While there:
- fix memory leak in case of error on values tap->chip,
  tap->tapname, tap->expected_ids;
- check for out of memory error;
- fix minor coding style issue;
- add the missing .usage field;
- remove functions not in use anymore.

Change-Id: I1c8c3ffeb324e9eacb919c7e0d94fd72122c9a81
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7431
Tested-by: jenkins

src/jtag/jtag.h

@@ -12,6 +12,7 @@
 #define OPENOCD_JTAG_JTAG_H
 
 #include <helper/binarybuffer.h>
+#include <helper/command.h>
 #include <helper/log.h>
 #include <helper/replacements.h>
 
@@ -602,6 +603,6 @@ void jtag_poll_unmask(bool saved);
 
 #include <jtag/minidriver.h>
 
-int jim_jtag_newtap(Jim_Interp *interp, int argc, Jim_Obj *const *argv);
+__COMMAND_HANDLER(handle_jtag_newtap);
 
 #endif /* OPENOCD_JTAG_JTAG_H */