iio: core: Replace lockdep_set_class() + mutex_init() by combined call

iio: core: Replace lockdep_set_class() + mutex_init() by combined call

[ Upstream commit c76ba4b2644424b8dbacee80bb40991eac29d39e ]

Replace lockdep_set_class() + mutex_init() by combined call
mutex_init_with_key().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Stable-dep-of: 9910159f0659 ("iio: core: add separate lockdep class for info_exist_lock")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>