iio: magnetometer: mmc35240: Fix a typo in the name of a constant

Everything is about mmc35240_ except MMC53240_WAIT_SET_RESET (3 and 5
switched).

This is likely a typo. Define and use MMC35240_WAIT_SET_RESET instead.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>