Fix iOS configurations

Replace ios_armv7 with ios only as they were all merged into one single
target.

Also, removing ios-x64-qt520-x86-conf as it was replaced with ios-x64-qt520-conf

Change-Id: I3081a93322135b191f384a65549b562d6c851259
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>