frameworks: add alwaysRequestAudioFocusForCalls overlay

https://github.com/CyanogenMod/android_frameworks_base/commit/64421f7d333881c5a34c849bae05bb182c2a18f8

fixing error:
frameworks/opt/telephony/src/java/com/android/internal/telephony/CallManager.java:538: cannot find symbol
symbol  : variable config_alwaysRequestAudioFocusForCalls