I don't know anything about International laws concerning Copywrit or Trademarks, but it seems that Radeon is a trademark of AMD. But according to Google Search concerning Trademark usages this is what it states:
Can I use a name already trademarked?
A business name generally can be protected as a trademark under federal and state trademark law. ... As a general rule, if someone in a similar field to yours is already using a particular business or organization name, you should not use it, nor should you use a name that would be confusingly similar.Since the Indian business has nothing to do with Computers, I guess it is fine to use unless AMD feels it may negatively impact their Trademark name. In which case they would need to use India's laws or apply international laws to get the company to stop using Radeon.
Also it is possible that the Indian Company received permission from AMD to use their Trademark name on a motor vehicle. This is one way for more of the public to be aware of RADEON thus indirectly advertising AMD.
Note: The word RADEON is a unique made up word that is not even listed in Dictionary.com.
