jtag: prepare for aligning switch and case statements

To prepare for aligning switch and case statements, fix in advance
some checkpatch error due to existing code:
- use '__func__' in place of hardcoded function name.

Change-Id: Ib90811c7fffa15702fb710345c5ca3c7331d5ad6
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/9052
Reviewed-by: zapb <dev@zapb.de>
Tested-by: jenkins

src/jtag/interface.c

@@ -86,8 +86,8 @@ int tap_move_ndx(enum tap_state astate)
 			ndx = 5;
 			break;
 		default:
-			LOG_ERROR("FATAL: unstable state \"%s\" in tap_move_ndx()",
-					tap_state_name(astate));
+			LOG_ERROR("FATAL: unstable state \"%s\" in %s()",
+					tap_state_name(astate), __func__);
 			exit(1);
 	}