Add a software codec based on the Fast Walsh Hadamard Transform.

The original FWHT codec was developed by Tom aan de Wiel, and it was
turned into 'proper' kernel code by Hans Verkuil, with a lot of
performance and memory improvements.
Signed-off-by: Tom aan de Wiel <tom.aandewiel@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>