fix missing scan symbol broken in previous kvs20xx commit

backend/kvs20xx.c

@@ -349,7 +349,7 @@ sane_start (SANE_Handle handle)
 	  if (st)
 	    return st;
 	}
-      st = scan (s);
+      st = kvs20xx_scan (s);
       if (st)
 	return st;
 

backend/kvs20xx_cmd.c

@@ -235,8 +235,8 @@ kvs20xx_reset_window (struct scanner * s)
   return send_command (s, &c);
 }
 
-static SANE_Status
-scan (struct scanner * s)
+SANE_Status
+kvs20xx_scan (struct scanner * s)
 {
   struct cmd c = {
     {0},

backend/kvs20xx_cmd.h

@@ -111,6 +111,7 @@ static const struct
   {
 3, 0x80, 9, SANE_STATUS_JAMMED},};
 
+SANE_Status kvs20xx_scan (struct scanner *s);
 SANE_Status kvs20xx_test_unit_ready (struct scanner *s);
 SANE_Status kvs20xx_set_timeout (struct scanner *s, int timeout);
 SANE_Status kvs20xx_set_window (struct scanner *s, int wnd_id);