Dual licensed package (dtc)

[Joe Davis <joe.davis512%gmail.com@localhost>]

Hi,

I'm working on adding U-Boot to pkgsrc as part of my work for Google
Summer of Code; I'm hoping to commit it to pkgsrc-wip sometime over
the next day or so.

One of the U-Boot's build time dependencies is `dtc` the linux
Device-Tree Compiler. Part of which is GPL, the other part of which is
a library, dual licensed under GPL/BSD.

I have to add dtc to pkgsrc-wip as well, so is it alright to denote
the entire package as simply being under the more restrictive GPL
license? Or is there a way that I should indicate a dual license?