src: use namespace prefix osmo_fd* and osmo_select*

Summary of changes:

s/struct bsc_fd/struct osmo_fd/g
s/bsc_register_fd/osmo_fd_register/g
s/bsc_unregister_fd/osmo_fd_unregister/g
s/bsc_select_main/osmo_select_main/g
diff --git a/openbsc/src/libcommon/socket.c b/openbsc/src/libcommon/socket.c
index dd25dd7..ff846aa 100644
--- a/openbsc/src/libcommon/socket.c
+++ b/openbsc/src/libcommon/socket.c
@@ -39,9 +39,9 @@
 #include <openbsc/gsm_data.h>
 #include <osmocom/core/talloc.h>
 
-int make_sock(struct bsc_fd *bfd, int proto,
+int make_sock(struct osmo_fd *bfd, int proto,
 	      uint32_t ip, uint16_t port, int priv_nr,
-	      int (*cb)(struct bsc_fd *fd, unsigned int what), void *data)
+	      int (*cb)(struct osmo_fd *fd, unsigned int what), void *data)
 {
 	struct sockaddr_in addr;
 	int ret, on = 1;
@@ -99,7 +99,7 @@
 		}
 	}
 
-	ret = bsc_register_fd(bfd);
+	ret = osmo_fd_register(bfd);
 	if (ret < 0) {
 		perror("register_listen_fd");
 		close(bfd->fd);