abis: add init function for emulated ipaccess/HSL emulated E1 input

This patch is a cleanup. It adds an init function for the ipaccess
and HSL emulated E1 input drivers.
diff --git a/openbsc/src/libabis/e1_input.c b/openbsc/src/libabis/e1_input.c
index 089d544..97dcd33 100644
--- a/openbsc/src/libabis/e1_input.c
+++ b/openbsc/src/libabis/e1_input.c
@@ -634,6 +634,8 @@
 
 void e1inp_misdn_init(void);
 void e1inp_dahdi_init(void);
+void e1inp_ipaccess_init(void);
+void e1inp_hsl_init(void);
 
 void e1inp_init(void)
 {
@@ -645,4 +647,6 @@
 #ifdef HAVE_DAHDI_USER_H
 	e1inp_dahdi_init();
 #endif
+	e1inp_ipaccess_init();
+	e1inp_hsl_init();
 }