Staging: w35und: Kill _USE_FALLBACK_RATE_ macro

The _USE_FALLBACK_RATE_ macro parametrizes DEFAULT_RATE_RETRY_LIMIT. It's only
used in Mxx_initial() in reg.c where _USE_FALLBACK_RATE_ is always defined
because the reg.c file includes sysdef.h at the top. It's therefore safe to
remove the _USE_FALLBACK_RATE_ macro.

Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>