pata_bf54x: decrease count first.

When count reaches 0 the postfix decrement still subtracts (to -1),
so bfin_reset_controller() returns as if the busy flag was cleared
while it was not.

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>