v4l2/mt9m114: remove dead code and adjust comments

v4l2/mt9m114: remove dead code and adjust comments

BZ: 24612

The mt9m114_poll_awhile() function is not used anywhere starting from at least
r2 branch. This patch removes it completely.

Comments related to mt9m114_write_reg_array() are moved closely to the
implementation.

Change-Id: Ie29dc1cc3187e00d705dbbd498f0c6d58faa9abc
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Acked-by: Tuukka Toivonen <tuukka.toivonen@intel.com>
Acked-by: David Cohen <david.a.cohen@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-on: http://android.intel.com:8080/36090
Reviewed-by: Shevchenko, Andriy <andriy.shevchenko@intel.com>
Reviewed-by: Cohen, David A <david.a.cohen@intel.com>
Reviewed-by: Wang, Wen W <wen.w.wang@intel.com>
Tested-by: Koski, Anttu <anttu.koski@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>