iio: bu27034: simplify using guard(mutex)

iio: bu27034: simplify using guard(mutex)

The BU27034 uses mutex for protecting the gain / time / scale changes.
The clean-up for a few of the functions can be slightly simplified by
removing the goto-based error handling/unlocking and by utilizing the
guard(mutex) scoped mutex handling instead.

Simplify driver by using the scoped mutexes.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/4e65a4725c211b166906f70fdb5ba90f2af0f570.1732193263.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>