[PATCH] smc91x: allow for dynamic bus access configs

All accessor's different methods are now selected with C code and unused
ones statically optimized away at compile time instead of being selected
with #if's and #ifdef's.  This has many advantages such as allowing the
compiler to validate the syntax of the whole code, making it cleaner and
easier to understand, and ultimately allowing people to define
configuration symbols in terms of variables if they really want to
dynamically support multiple bus configurations at the same time (with
the unavoidable performance cost).

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>