sound/oss/trident.c: fix incorrect test in trident_ac97_set()

If count reaches zero, the loop ends, but the postfix decrement still
subtracts: testing for 'count == 0' will not work.

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Reviewed-by: Ray Lee <ray-lk@madrabbit.org>
Acked-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>