Removed warning: `dev_io_fd' defined but not used. Variable used only by

FreeBSD. Added test for FreeBSD. Patch from Stephen Torri <storri@ameritech.net>.
Henning Meier-Geinitz <henning@meier-geinitz.de>

sanei/sanei_ab306.c

@@ -99,7 +99,9 @@ inb (u_long port)
 #define PORT_DEV	"/dev/port"
 #define AB306_CIO	0x379		/* control i/o port */
 
+#if defined(__FreeBSD__)	
 static int dev_io_fd = 0;
+#endif
 
 typedef struct port
   {