Staging: silicom: remove the board_t typedef in bpctl_mod.c

Replace the board_t enum typdef with struct board_type (_type for
consistency with media_type, above), resolving a checkpatch.pl
warning. (As far as I can tell, this isn't used anywhere.)

Signed-off-by: Chad Williamson <chad@dahc.us>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>