gbproxy: Check tlli_info when patching, fix APN patching

Currently the numeric TLLI or tlli_info's enable_patching flag is
used to decide, whether a APN shall be patched or the secondary SGSN
shall be used. Using the numeric TLLI imposes a problem, when
TLLI/P-TMSI patching is used, since gbproxy_check_tlli uses the BSS
side TLLI namespace when trying to get the tlli_info.

This patch modifies the gbproxy_check_tlli() function to accept a
tlli_info pointer instead of a numeric TLLI. The tlli_info is already
available when the function is called. Since this a similar approach
has been used by accessing the enable_patching flag directly, this
commit unifies checking by always using this function instead of the
flag outside of gb_proxy_tlli.c.

This fixes the APN patching that doesn't work currently when P-TMSI
patching is enabled.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index 2026d1a..e77d527 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -330,7 +330,7 @@
 
 	tlli_info = gbproxy_update_tlli_state_ul(peer, now, &parse_ctx);
 
-	if (tlli_info && tlli_info->enable_patching && cfg->route_to_sgsn2) {
+	if (tlli_info && cfg->route_to_sgsn2 && gbproxy_check_tlli(peer, tlli_info)) {
 		sgsn_nsei = cfg->nsip_sgsn2_nsei;
 		send_msg_directly = 1;
 	}