{enb,ms}_srs: Add DL QAM-256 support

Due to the integration of DL-QAM256 another table for DL max rates is needed.
Therefore, I added the parameter 'qam256' to the feature list in the resource.cfg.

The patch also enables the correct UE settings in the config file.

Change-Id: I2d34395449cdcfb31db66ea887d9adbee551e757
diff --git a/src/osmo_gsm_tester/templates/srsue.conf.tmpl b/src/osmo_gsm_tester/templates/srsue.conf.tmpl
index 284922b..31642cd 100644
--- a/src/osmo_gsm_tester/templates/srsue.conf.tmpl
+++ b/src/osmo_gsm_tester/templates/srsue.conf.tmpl
@@ -150,6 +150,10 @@
 % if int(ue.num_carriers) > 1:
 ue_category       = 7
 release           = 10
+% elif "dl_qam256" in ue.features:
+ue_category       = 7
+release           = 13
+ue_category_dl    = 14
 % else:
 #ue_category       = 4
 #release           = 8