procd: start additional consoles during hotplugging

Now that 'start-console' procd command has reached the main repo,
we can add a rule to start consoles on serial devices which are
created when USB gadget driver reports creation with hotplugging.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

package/system/procd/files/hotplug.json

@@ -37,6 +37,10 @@
 					[ "load-firmware", "/lib/firmware" ],
 					[ "return" ]
 				]
+			],
+			[ "if",
+				[ "regex", "DEVNAME", "^ttyGS" ],
+				[ "start-console", "%DEVNAME%" ]
 			]
 		],
 		"remove" : [