telephony: SignalStrengh: Don't calculate a LTE snr if the srq is invalid

If the previous values are invalid and signal quality is -1, chances are there's
no LTE signal at all, so don't calculate the SNR and mark it invalid as well.

This fixes the strength indicator in GSM devices where it was being skewed
by the ghost LTE value

Change-Id: I070573401c141aa99941a332ee256246697abb90
Telephony: Add getLteOnGsmMode() method (1/2)

Same functionality as the existing getLteOnCdmaMode, but for GSM
LTE devices.
Enable with the telephony.lteOnGsmDevice system property

From CM 10.0: Ibfb47ca608e51393b99d3308e0a6c66050b3f32e
- Moved getLteOnGsmModeStatic() to TelephonyManager.
readd removed audio files
core and telephony: Additional HSPAP support

Change-Id: I5e921d2308d873678d6ef67a91cff50d383a176b
Framework: Fix GSM signal strength

Certain OEM gsm ril libs send back a bogus value for LTE signal
that causes SignalStrength.java to default to LTE and report
incorrect signal values.
Use prop value ro.telephony.ril.v3=signalstrength to get proper
GSM signal reading on certain devices.

Change-Id: Ibb23d7b3a2d21001ccbbc6ebfbdc3c5248f18cfc
Signed-off-by: dhacker29 <davidhackerdvm@gmail.com>

Conflicts:
	telephony/java/android/telephony/SignalStrength.java
telephony: hide needsOldRilFeature

Change-Id: I741b510fdacc166ad40741bf2e9db5c8a1039384