staging:iio:ad2s1210: Rework read/write operation for fclkin and fexin

This patchset changes the way that frequency of clock input (fclkin) and the excitation frequency (fexcit) are exposed to the userspace. The original code uses the IIO_DEVICE_ATTR to export the configuration of fclkin and fexcit to the userspace which is not in agreement with the current ABI. This patchset adds one channel per clock configuration, updating the read_raw function by adding a handler for the new channels, and introduces the write_raw function. Furthermore, this patchset removes the legacy code responsible for the read and write operation related to fclkin and fexcit. Finally, this patchset uses parts of the original code for handling frequency configuration as an attempt to avoid problems.

Changes in v2:
- Removes unnecessary switch case in the write_raw function.
- Replaces the use of goto for direct return.
- Removes definition with string.
- Removes unecessary label.

Rodrigo Siqueira (3):
staging:iio:ad2s1210: Add channel for fclkin and fexcit staging:iio:ad2s1210: Add frequency handler in read_raw staging:iio:ad2s1210: Add write_raw to handle frequency

 drivers/staging/iio/resolver/ad2s1210.c | 191 +++++++++++++++-----------------
 1 file changed, 92 insertions(+), 99 deletions(-)

2.16.2