docs: devices.rst: get rid of :c:type macros

There's no need to use macros to use :c:type on this file,
as automarkup.py should do this automatically.

Also, this breaks compatibility with Sphinx 3.x, as there,
structs should be declared using .. c:struct.

So, get rid of them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>