media: v4l2: remove remaining compat_ioctl

There are no remaining conversions in v4l2_compat_ioctl32(),
so all the infrastructure for it can be removed, with the
only remaining bit being the compat_ioctl32() callback into
drivers that implement their own incompatible data structures.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>