Blackfin: bfin_sdh: set all timer bits before transfer

The timer register is 32bits, not 16bit, so 0xFFFF won't fill it.
Write out -1 to make sure to fill the whole thing.

Signed-off-by: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>