MIPS: DTS: ingenic/qi,lb60: Add model and memory node

Add a memory node, which was missing until now, and use the retail name
"Ben Nanonote" as the model, as it is way more known under that name
than under the name "LB60".

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>