staging: iio_simple_dummy: fix module_param type

Fix the module_param "instances" type to uint, since the variable type
holding the value is unsigned.

Signed-off-by: Vladimirs Ambrosovs <rodriguez.twister@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --cc drivers/staging/iio/iio_simple_dummy.c
Simple merge