Add modem resource features attributes: 2g, 3g, 4g

This allows selecting modem by supported network type. It will allow
using 4G modems with type different than srsue in 4g suite in the future.

Change-Id: I38bcf6abf789f52c3ed0bee7911567fa872e2491
diff --git a/example/resources.conf.rnd b/example/resources.conf.rnd
index 5358a61..4ce39d1 100644
--- a/example/resources.conf.rnd
+++ b/example/resources.conf.rnd
@@ -74,28 +74,28 @@
   ki: '80A37E6FDEA931EAC92FFA5F671EFEAD'
   auth_algo: 'comp128v1'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd', 'sim']
+  features: ['2g', 'sms', 'voice', 'ussd', 'sim']
 
 - label: sierra_2nd
   path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.3'
   ki: '00969E283349D354A8239E877F2E0866'
   auth_algo: 'comp128v1'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd', 'sim']
+  features: ['2g', 'sms', 'voice', 'ussd', 'sim']
 
 - label: ec20_1
   path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.6'
   ki: 'BB70807226393CDBAC8DD3439FF54252'
   auth_algo: 'comp128v1'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd', 'gprs', 'sim']
+  features: ['2g', 'sms', 'voice', 'ussd', 'gprs', 'sim']
 
 - label: ec20_2
   path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.5'
   ki: '2F70DCA43C45ACB97E947FDD0C7CA30A'
   auth_algo: 'comp128v1'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd', 'gprs', 'sim']
+  features: ['2g', 'sms', 'voice', 'ussd', 'gprs', 'sim']
 
 osmocon_phone:
 - serial_device: '/dev/serial/by-id/usb-Silicon_Labs_CP2104_USB_to_UART_Bridge_Controller_0089279D-if00-port0'