arm_adi_v5: Fix dap apsel confusing behaviour.

Make dap apsel without arguments show current state instead of changing
to AP 0.

Change-Id: I75ea10e3e1b8a067f2dc417ec6691dc7ceec1af6
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/3163
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/target/arm_adi_v5.c

@@ -1541,7 +1541,7 @@ COMMAND_HANDLER(dap_apsel_command)
 
 	switch (CMD_ARGC) {
 	case 0:
-		apsel = 0;
+		apsel = dap->apsel;
 		break;
 	case 1:
 		COMMAND_PARSE_NUMBER(u32, CMD_ARGV[0], apsel);