iio: inkern: put the IIO device when it fails to allocate memory

 The reference count of the IIO device is increased if the IIO map has
 matched consumer name.
 After then, it tries to allocate the iio_channel which is used by the consumer.
 If it fails to allocate memory, the reference count should be decreased.

 This patch enables restoring the reference count of the IIO device.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>