CDMA voicemail notification fixes

1.  Convert the voicemail count of a VM notification from
    BCD to decimal. That way the user will not be notified
    of 16 new VM when there are only 10.
    Ref: 3GPP2 C.S0015-B / 4.5.12 Number of Messages.
2.  Allow VMN-95 notifications without "User Data" to be
    processed. Only mandatory items for VMN-95 are
    "Message Identifier" and "Number of Messages".
    Ref: 3GPP2 C.S0015-B / 4.3.5 Voice Mail Notification.