iio: ABI: Fix wrong format of differential capacitance channel ABI.

iio: ABI: Fix wrong format of differential capacitance channel ABI.

BugLink: https://bugs.launchpad.net/bugs/1996825
[ Upstream commit 1efc41035f1841acf0af2bab153158e27ce94f10 ]

in_ only occurs once in these attributes.

Fixes: 0baf29d658c7 ("staging:iio:documentation Add abi docs for capacitance adcs.")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220626122938.582107-3-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>