iio: meter: ina3221: update ina3221 driver

iio: meter: ina3221: update ina3221 driver

This patch includes following fixes and updates to ina3221 driver:
  * Fix handling of critical and warning alert registers.
  * Add check of "conversion ready flag" bit when performing triggered
    conversions.
  * Add code to prevent changes between TRIGGERED and CONTINUOS when
    critical or warning alert is not being set.

Change-Id: I79a704c58619be27dc4dfa1aec556ae8e382ecfa
Signed-off-by: Timo Alho <talho@nvidia.com>
Reviewed-on: http://git-master/r/390158
(cherry picked from commit 7f77e3167163fffad8146c07a86b0aa6eb98ce77)
Reviewed-on: http://git-master/r/390163
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>