e1d: Initial osmo-e1d support

osmo-e1d is part of the Osmocom 'software defined E1 interface,
which consists of a USB device for the actual E1 hardware interfacing,
and a daemon (osmo-e1d) implementing a libusb-based driver.

This commit adds initial support for talking to osmo-e1d using
the related libosmoe1d library.  You need to use '--enable-e1d'
at configure time to enable it.

Change-Id: Ia0431c124e3b5b4108aee7b109d8c4bb0d8b45d4
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/abis/e1_input.h b/include/osmocom/abis/e1_input.h
index de1c504..00b4aaa 100644
--- a/include/osmocom/abis/e1_input.h
+++ b/include/osmocom/abis/e1_input.h
@@ -129,6 +129,10 @@
 			struct osmo_fd fd;
 		} dahdi;
 		struct {
+			/* osmo-e1d driver has one fd for each ts */
+			struct osmo_fd fd;
+		} e1d;
+		struct {
 			struct osmo_fd fd;
 		} rs232;
 	} driver;