Fix warnings

sound/oss/davinci-audio.c:154: warning: initialization from
incompatible pointer type
sound/oss/davinci-audio.c:155: warning: initialization from
incompatible pointer type
Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
Signed-off-by: Kevin Hilman <khilman@mvista.com>