external/qemu: Support for Signal Strength in emulator

Change-Id: Ia62ef338b64739d50eeb55d33d15227a0047d8d0
Merge pull request #30 from EdgarChen/bug_869327

Bug 869327 - B2G Emulator: Upgrade hardware/ril, external/qemu to include RILv7/CDMA. r=vicamo
Cherry-picked from commit 8c4699985ec66961231542d8133868a3864bf39e