target/riscv: support for smp group manipulation

this functionality allows to query if a target belongs to some smp group
and to dynamically turn on/off smp-specific behavior

Change-Id: I67bafb1817c621a38ae4a2f55e12e4143e992c4e
Signed-off-by: Parshintsev Anatoly <anatoly.parshintsev@syntacore.com>
Signed-off-by: Bernhard Rosenkränzer <bero@baylibre.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8296
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/riscv/riscv.c

@@ -3049,6 +3049,9 @@ static const struct command_registration riscv_command_handlers[] = {
 		.usage = "",
 		.chain = semihosting_common_handlers
 	},
+	{
+		.chain = smp_command_handlers
+	},
 	COMMAND_REGISTRATION_DONE
 };