sound: oss: avoid time_t usage

We want to remove all time_t users from the kernel because of
y2038 compatibility. This particular instance does not even
use time_t to store a seconds value, so we can simply use
'unsigned int', which seems more fitting anywhere.

The same code is used in two OSS files.

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