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.

Signed-off-by: Yann Dirson <yann@blade-group.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit e332738a)
Signed-off-by: Steve Sakoman <steve@sakoman.com>