Running generic_buffer without enabling any channel of the
sensor will fail without printing any error message.

Add an error message that indicates buffer enable failed.
Signed-off-by: NIrina Tirdea <irina.tirdea@intel.com>
Acked-by: NHartmut Knaack <knaack.h@gmx.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>