tty: rocket: fix incorrect forward declaration of 'rp_init()'

Make the forward declaration actually match the real function
definition, something that previous versions of gcc had just ignored.

This is another patch to fix new warnings from gcc-9 before I start the
merge window pulls.  I don't want to miss legitimate new warnings just
because my system update brought a new compiler with new warnings.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/tty/rocket.c

@@ -266,7 +266,7 @@ MODULE_PARM_DESC(pc104_3, "set interface types for ISA(PC104) board #3 (e.g. pc1
 module_param_array(pc104_4, ulong, NULL, 0);
 MODULE_PARM_DESC(pc104_4, "set interface types for ISA(PC104) board #4 (e.g. pc104_4=232,232,485,485,...");
 
-static int rp_init(void);
+static int __init rp_init(void);
 static void rp_cleanup_module(void);
 
 module_init(rp_init);