gdb: remove TYPE_MAIN_TYPE

IMO, there is no point in keeping this macro.  Remove it and access the
field directly.  If we ever want some kind of abstraction in front of
the field, then we'll add a method.

Change-Id: I1076b0e07644afdc0c1f3a4916148d3344a9d395
Approved-By: Andrew Burgess <aburgess@redhat.com>
6 files changed