tools:iio:lsiio: add error handling

Add error handling to calls which can indicate a major problem by
returning an error code.
This also involves to change the type of dump_devices() from void to int.

Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
1 file changed