We cannot install different opaque pointer for read and write
of the same i/o address.
- handle zero address in bmdma_writeb_common and install
the same opaque pointer for both read and write access.
Signed-off-by: Igor V. Kovalenko <igor.v.kovalenko@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>