Mms: MMS ui fixes for lineNumber and mobileDataEnabled flag.

- Use the linenumber of the subscription as selected from prompt.
- Request PDP activation irrespective of MobileData enable/disable.
Framework would ultimately decide based on resource config if PDP is
allowed or not.

Change-Id: If22f7b9ee04341c8312875a2b52e737b1ab5b0a1