of: Update Moxa vendor prefix description

Update vendor description to be the full name of the corporate entity
with this prefix

reference:
[1]: http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4806:26uh56.2.5



Signed-off-by: SZ Lin <sz.lin@moxa.com>
Signed-off-by: Rob Herring <robh@kernel.org>