dt: amd-seattle: remove Husky platform

The Huskyboard never made it to production, and its successor the
Celloboard was only shipped in very limited quantities with ACPI
only firmware, so the historical significance of husky.dts is
highly questionable. Let's drop it.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>