media: ca-get-descr-info.rst: document this ioctl

Instead of a generic boilerplate, fill it with relevant
information about this ioctl.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Mauro Carvalho Chehab 2017-09-01 08:39:43 -04:00
commit e0f891d846