jz47xx: fix plugins/codec link address
Removing STUBOFFSET in commit 78542df4666 caused DRAMSIZE
to be computed incorrectly, not taking into account the
16k offset used for 'IRAM'. As a result plugins & codecs
got shifted 16k upwards from their intended load address,
making them unable to load.
Change-Id: I6c338e04506e12fa2b8a69286a1ed785a2f8042d