improve a calculation method for LTE antenna reception level

Current calculation uses a RSSNR value but it is unsuitable
for accurate reception level.
(The measurement requirement for RSSNR does not exist in 3GPP.)
Instead, it should use a RSRQ value defined by 3GPP
specification: TS 36.214.

The minimum level of RSRQ required to display Antenna icon
should be the minimum value of Qqualmin which is a minimum
required RSRQ defined by 3GPP specification: TS 36.331 RRC.

Also RSRP value thresholds is relatively high compared with
other mobile phone platforms, which make android seems
low sensitive to radio. This patch sets better thresholds.

Change-Id: I502e1c3d08b2a52c51fe93da9b77476ac827a25b