Nested submodule and port list accesses do not translate correctly

[dmlockhart]

Code that has two subscript operators like so:

  s.mod[0].port_list[0]

Fails if port_list is a list of ports.

Note that the following scenario (bit slicing a port that is not in a port list) works fine:

  s.mod[0].single_port[0]

Things that fail:

• list-index of a port-list accessed via a module list (mod[i].port_list[j])

Things to check:

• bit-index of a port accessed via a port-list (mod.port_list[i][j])
• bit-index of a port accessed via a port-list accessed via a module list (mod[i].port_list[j][k])
• list-index of a 2-D port-list (mod.port_list[i][j])
• bit-index of a port accessed via 2-D port-list (mod.port_list[i][j][k])
• port accessed from a 2-D module-list (mod[i][j].port)
• bit-index of a port accessed from a 2-D module-list (mod[i][j].port[k])
• etc...

Things that work:

• bit-index of a port accessed via submodule list (mod[i].single_port[j])