iio: imu: inv_icm45600: Initializes inv_icm45600_buffer_postdisable() sleep

iio: imu: inv_icm45600: Initializes inv_icm45600_buffer_postdisable() sleep

The sleep variable in inv_icm45600_buffer_postdisable() could be used without
being assigned in case of error. It must be initialized to 0 by default.

Fixes: 06674a72cf7a ("iio: imu: inv_icm45600: add buffer support in iio devices")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-iio/aPi6Xw-ZoUkW76zR@stanley.mountain/
Signed-off-by: Remi Buisson <remi.buisson@tdk.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>