[LLDB] Fix "memory region --all" when there is no ABI plugin

There are two conditions for the loop exit. Either we hit LLDB_INVALID_ADDRESS
or the ABI tells us we are beyond mappable memory.

I made a mistake in that second part that meant if you had no ABI plugin
--all would stop on the first loop and return nothing.

If there's no ABI plugin we should only check for LLDB_INVALID_ADDRESS.

Depends on D134029

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D134030