Yes it is possible to describe RTL and TLM within the same component using two different views. The motivation to have more than one view is that you can describe multiple implementations of an IP in the same IP-XACT component.
The way to indicate if a port is present is a particular view is to use the wireTypeDefs (for wire ports) and transTypeDefs (for transactional ports). Each wireTypeDef and each transTypeDef contains zero or more viewRef elements. If there are zero viewRef elements then the type applies to all views (implying that the port is present is all views). If there are one or more viewRef elements then the type applies only to the views specified by the viewRef elements (implying that the port is not present in the views that are not specified). If a port does not have wireTypeDefs or transTypeDefs then the default type applies to all views (implying that the port is present in all views).
I must admit that this is not very well described in the IEEE 1685-2014 document in Sections 6.12.9 and 6.12.19.