fix commit "update hisim to version 2.7.0"

missing #include "ngspice/config.h"

thats required for consistent interpretation of the type
  struct IFdevice
from ngspice/ifsim.h
included from ngspice/devdefs.h

(invisible XSPICE definition leading
   to different size and layout of this struct)

src/spicelib/devices/hisim2/hsm2init.c

@@ -1,3 +1,5 @@
+#include "ngspice/config.h"
+
 #include "ngspice/devdefs.h"
 
 #include "hsm2def.h"