trx: detect UL SID in EFR just like in FR

The TCH/F Rx code in osmo-bts-trx uses osmo_fr_check_sid() to detect
when the MS sends SID, and passes the flag to lchan_set_marker().
However, equivalent logic was missing for EFR, as until recently
there was no EFR SID check function in libosmocodec.  Now that
we have osmo_efr_check_sid(), use it.

Change-Id: Ib043e00dbf92145c2a6c32f6365517244472a922
---
M TODO-RELEASE
M src/osmo-bts-trx/sched_lchan_tchf.c
2 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/TODO-RELEASE b/TODO-RELEASE
index 1833716..88ad00d 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -7,4 +7,5 @@
 # If any interfaces have been added since the last public release: c:r:a + 1.
 # If any interfaces have been removed or changed since the last public release: c:r:0.
 #library	what	        description / commit summary line
+libosmocodec	>1.8.0		osmo_efr_check_sid() new function
 libosmogsm	>1.8.0		<osmocom/gsm/protocol/gsm_44_060.h> added
diff --git a/src/osmo-bts-trx/sched_lchan_tchf.c b/src/osmo-bts-trx/sched_lchan_tchf.c
index eff0f63..256125b 100644
--- a/src/osmo-bts-trx/sched_lchan_tchf.c
+++ b/src/osmo-bts-trx/sched_lchan_tchf.c
@@ -150,6 +150,8 @@
 		break;
 	case GSM48_CMODE_SPEECH_EFR: /* EFR */
 		rc = gsm0503_tch_fr_decode(tch_data, *bursts_p, 1, 1, &n_errors, &n_bits_total);
+		if (rc == GSM_EFR_BYTES) /* only for valid *speech* frames */
+			lchan_set_marker(osmo_efr_check_sid(tch_data, rc), lchan); /* DTXu */
 		break;
 	case GSM48_CMODE_SPEECH_AMR: /* AMR */
 		/* the first FN 0,8,17 defines that CMI is included in frame,

