Initialize maxActiveVoiceSubscriptions to maxActiveInternetData

- maxActiveData defines how many logical modems can have internet
 PDN connections simultaneously. For L+L DSDS modem it’s 1, and
 for DSDA modem it’s 2.
- Since PhoneCapability.aidl does not have a dedicated field for
  maxActiveVoiceSubscriptions, this is a reasonable default.

Test: Boot up device and confirm PhoneCapability values
Fix: 254926322
Change-Id: I21f7aa58a0c97e66365cfb3b84871d28ba85d22c