resources.conf: sierra modems support gprs

At least the signalling support we are currently running, so let's add
the gprs feature to them as they can be used to run the current tests.

Change-Id: I04459786ba76813ebaa7867bcc86afb4fa9700b9
diff --git a/example/resources.conf b/example/resources.conf
index c1ab322..1672d91 100644
--- a/example/resources.conf
+++ b/example/resources.conf
@@ -73,7 +73,7 @@
   ki: '80A37E6FDEA931EAC92FFA5F671EFEAD'
   auth_algo: 'xor'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd']
+  features: ['sms', 'voice', 'ussd', 'gprs']
 
 - label: sierra_2
   path: '/sierra_2'
@@ -81,7 +81,7 @@
   ki: '00969E283349D354A8239E877F2E0866'
   auth_algo: 'xor'
   ciphers: [a5_0, a5_1]
-  features: ['sms', 'voice', 'ussd']
+  features: ['sms', 'voice', 'ussd', 'gprs']
 
 - label: ec20
   path: '/gobi_0'