staging: brcm80211: removed more unused dma32 code

Since two preprocessor defines are always '1', could remove code that was
never compiled in and removed references to these preprocessor defines
(DMA64_ENAB and DMA64_MODE).

Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>