doc-rst: vidioc-queryctl: change the title of this chapter

This chapter is referenced on several parts of the extended
controls. Change the title to make it nicer where it is
referenced.

Ok, we might, instead, just change the name for the references
to only mention the oldest ioctl, but IMHO, it is better to
keep the name of all ioctls where it is referenced.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>