linux-firmware: include all relevant files in -bcm4356

This currently catches the .clb_blob and .vamrs,rock960.txt, and other
.txt files may come in future upstream releases.

(From OE-Core rev: 501cd3063af388dabd3329d2e69ac218ffd62a9e)

Signed-off-by: Yann Dirson <yann@blade-group.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit e332738a8aae0914c58b40faae8b9d7a82fd6a95)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>