iio: magnetometer: ak8974: remove redundant zero timeout check

At the end of the delay loop timeout will always be zero
and hence the check for !timeout will always be true. Remove
the redundant check and the redundant return 0 at the end of
the function.

Fixes CoverityScan CID#1357168 ("Logically dead code")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>