iforce compilation fixes for 2.5.25

[Brad H. <bh...@bi...>]

The iforce code in 2.5.25 won't compile unless both USB and RS232 versions are 
built into the kernel.

This patch fixes the two issues:
1. IFORCE_232 and IFORCE_USB are used in iforce-packet.c without testing if 
they exist.
2. IFORCE_232 needs to be defined when the Config.in option is set as a module 
or when built into the kernel. Same for IFORCE_USB.

Brad

-- 
http://conf.linux.org.au. 22-25Jan2003. Perth, Australia. Birds in Black.