sound: oss/dmabuf: use dma_map_single

The virt_to_bus/bus_to_virt functions have been deprecated
for as long as I can remember, and they are used in very
few remaining instances, usually in obscure ISA device
drivers. The OSS sound drivers are the only ones that are
still used on the ARM architecture, and only on some of
the earliest StrongARM machines.

The problem for converting the OSS subsystem to use
dma_map_single instead is that the caller of virt_to_bus
does not have a device pointer, since the subsystem has
never been ported to use the common device infrastructure.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>