dBm signal text CDMA fix

* refactored calculations, instead of having another phone listener in the
  cmsignaltext class, it now broadcasts an intent with the dbm value
  using the same calculations as the Settings > About screen.

* moved calculations in updateSignalStrenght() to the top so if there's no
  sim card it will still show a proper dbm (otherwise it will show 0).
  Do we want to show the dBm AND a "no signal" bars icon in this case?

  patch 2: using intents to pass dbm value now
  patch 3: remove extra white space
  patch 4: using the same dbm calculations as Settings > About screen

Change-Id: Ief6d767f8255b7a3c6857f5581eb77e950e71598
Signed-off-by: Roman Birg <romanbirg@gmail.com>