Build one osmo-trx binary for each device support enabled

Same way as we do in osmo-bts. After this commit, osmo-trx no longer
exists. Instead, osmo-trx-uhd and osmo-trx-usrp1 are generated based on
configure flags enabled.

A new flag --with(out)-uhd has been added to enable/disable build of
osmo-trx with UHD backend. It is left enabled by default to keep
compatibility with older build scripts. Binary with USRP1 backend must
still be manually enabled with --with-usrp1 flag.

Change-Id: Iea8c0d7434762713a53440d29bf3ebd84accb262
diff --git a/debian/osmo-trx-uhd.install b/debian/osmo-trx-uhd.install
new file mode 100644
index 0000000..0005b76
--- /dev/null
+++ b/debian/osmo-trx-uhd.install
@@ -0,0 +1 @@
+/usr/bin/osmo-trx-uhd