Introduce BS and MS power control related functions

* add bts->band field plus corresponding VTY and commandline argument
* add trx->nominal_power and trx->max_power_red fields
* add rsl_chan_bs_power_ctrl() to control TRX RF power for a given TS
* add rsl_chan_ms_power_ctrl() to control MS RF power for a given lchan.
diff --git a/openbsc/include/openbsc/abis_rsl.h b/openbsc/include/openbsc/abis_rsl.h
index 532595b..c928ffa 100644
--- a/openbsc/include/openbsc/abis_rsl.h
+++ b/openbsc/include/openbsc/abis_rsl.h
@@ -411,5 +411,8 @@
 int rsl_ccch_conf_to_bs_ccch_sdcch_comb(int ccch_conf);
 int rsl_number_of_paging_subchannels(struct gsm_bts *bts);
 
+int rsl_chan_bs_power_ctrl(struct gsm_lchan *lchan, unsigned int fpc, int db);
+int rsl_chan_ms_power_ctrl(struct gsm_lchan *lchan, unsigned int fpc, int dbm);
+
 #endif /* RSL_MT_H */