Don't use SNR in the invalid check.

Since some RILs use -1 instead of INVALID_SNR as invalid vlue for
LTE SNR, SignalStrength will not use LTE SNR to check if LTE valid.

bug:5970403
Change-Id: Ia948e076f8f5878e081e87680076b187857879c8

Author: John Wang

telephony/java/android/telephony/SignalStrength.java

@@ -293,10 +293,11 @@ public int getLevel() {
         int level;
 
         if (isGsm) {
+            // TODO Need solve the discrepancy of invalid values between
+            // RIL_LTE_SignalStrength and here.
             if ((mLteSignalStrength == -1)
                     && (mLteRsrp == -1)
                     && (mLteRsrq == -1)
-                    && (mLteRssnr == INVALID_SNR)
                     && (mLteCqi == -1)) {
                 level = getGsmLevel();
             } else {
@@ -331,7 +332,6 @@ public int getAsuLevel() {
             if ((mLteSignalStrength == -1)
                     && (mLteRsrp == -1)
                     && (mLteRsrq == -1)
-                    && (mLteRssnr == INVALID_SNR)
                     && (mLteCqi == -1)) {
                 asuLevel = getGsmAsuLevel();
             } else {
@@ -367,7 +367,6 @@ public int getDbm() {
             if ((mLteSignalStrength == -1)
                     && (mLteRsrp == -1)
                     && (mLteRsrq == -1)
-                    && (mLteRssnr == INVALID_SNR)
                     && (mLteCqi == -1)) {
                 dBm = getGsmDbm();
             } else {