Removed printf noise in channel.c

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
IIOD: Update call to iio_device_read_raw, as its prototype changed

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
IIOD: Use function iio_device_open instead of iio_device_open_mask

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
Remove API function iio_device_open_mask

This function is now used internally, but is not anymore part of
the API.

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
Store the channel mask in the iio_device structure

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
Change prototype of API function iio_device_get_sample_size

This function no more requires a channel mask to be passed as
parameter; instead, it will use the one stored in the iio_device
structure.

As it is still needed at some places, the private function
iio_device_get_sample_size_mask has been introduced, which works
exactly like the previous iio_device_get_sample_size.

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
IIOD: Update call to iio_device_get_sample_size as its prototype changed

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>