vty: Introduce API vty_read_config_filep

This new API doesn't use host_config_set(), and allows passing a FILE*
from any source, not only a filesystem path.

Related: SYS#5369
Change-Id: I720ac04386261628c0798a1bfcaa91e2490a86c3
diff --git a/include/osmocom/vty/vty.h b/include/osmocom/vty/vty.h
index d34433f..3e6178f 100644
--- a/include/osmocom/vty/vty.h
+++ b/include/osmocom/vty/vty.h
@@ -141,7 +141,7 @@
 #define TELNET_NAWS_SB_LEN 5
 	/*! sub-negotiation buffer */
 	unsigned char sb_buf[TELNET_NAWS_SB_LEN];
-	/*! How many subnegotiation characters have we received?  
+	/*! How many subnegotiation characters have we received?
 	 *
 	 * We just drop those that do not fit in the buffer. */
 	size_t sb_len;
@@ -210,6 +210,7 @@
 /* Prototypes. */
 void vty_init(struct vty_app_info *app_info);
 int vty_read_config_file(const char *file_name, void *priv);
+int vty_read_config_filep(FILE *confp, void *priv);
 void vty_init_vtysh (void);
 void vty_reset (void);
 struct vty *vty_new (void);