Fix .ncbss from possibly overlapping .ncdata in plugins/codecs.
(Take #2)
If .bss wasn't large enough, and .ncdata was empty, .ncbss would be
at an address overlapping the alignment-padded end of .ncdata and
and linking would fail with an overlap error.
Adds plugin load end address that accounts for IRAM going past
the final .bss sections, making IRAM overlay compatible. load_code
could also use this instead of the file size.
The .lds becomes a bit more straightforward and explicit when
assigning addresses.
Change-Id: Id0c33f257710e97ece2c831e0feaaa32c1a14e05