staging: iio: light: iqs253: update sensor code

staging: iio: light: iqs253: update sensor code

1. clean up obsolete code paths
2. modify init sequence
3. modify i2c communication protocol
4. re init on power on reset detection
5. modify proximity detection thresholds and ATI registers

Bug 1499925

Change-Id: Icd81346259e5e689ce64854a421b6e53f1d67d05
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/427154
(cherry picked from commit ae2861e7b8439574e36b0ccd41bf9e07a7c4a964)
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/434893
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>