staging:iio:ade7758: Remove "raw" from channel name

commit b598aacc29331e7e638cd509108600e916c6331b upstream.

"raw" is a property of a channel, but should not be part of the name of
channel.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
[bwh: Backported to 3.2: using IIO_CHAN() macro to initialise the structures]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>