Staging: spectra: removes q->prepare_flush_fn, fix build breakage

This patch is the first one of a patchset that allows 
stagin/spectra driver to compile in linux-next. 

blk_queue_ordered doesn't receive a prepare flush function anymore

Signed-off-by: Javier Martinez Canillas <martinez.javier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>