libril: revert network operator string handling

libril: revert network operator string handling

* These workarounds were introduced before http://review.cyanogenmod.org/#/c/159520/
  and are no longer needed because the framework now has dynamic QAN element support.
  Setting the ro.ril.telephony.mqanelements to a proper value should fix the operator
  search on all the devices and these workarounds are no longer required.

* http://review.cyanogenmod.org/#/c/100398/ discards every 5th QAN element which breaks
  devices with libsec-ril that returns more than 5 QAN elements. zeroflte and noblelte
  return 6 QAN elements and the 5th element was being discarded instead of 6th.

* The code assumes 5 QAN elements per operator which doesn't hold true for all devices.

* In case of devices with 6 QAN elements, the size of the string array was a multiple
  of 6, but since we are discarding the 5th element, the contents of the string pertaining
  to each operator is a multiple of 5 following by trailing null strings in the array,
  which caused issues in the framework while trying to read the strings, since we are
  expecting 6 strings per operator and with a discarded string, we only receive 5.

Thanks to Javi Ferrer for diagnosing the issue on zeroflte

Change-Id: I2e99291f3438998a253755a19a063d15a19d63e0