iio: gyro: adxrs290: Use guard(mutex) in lieu of manual lock+unlock

iio: gyro: adxrs290: Use guard(mutex) in lieu of manual lock+unlock

Use guard(mutex)() to automatically release the lock on scope exit,
simplifying the error handling path and removing the need for
explicit unlock and goto-based cleanup.

Signed-off-by: Guilherme Dias <guilhermeabreu200105@usp.br>
Co-developed-by: João Paulo Menezes Linaris <jplinaris@usp.br>
Signed-off-by: João Paulo Menezes Linaris <jplinaris@usp.br>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Maxwell Doose <m32285159@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>