V4L/DVB: Dvbdev: fix illegal re-usage of fileoperations struct

V4L/DVB: Dvbdev: fix illegal re-usage of fileoperations struct

Arjan van de Ven <arjan@infradead.org> reported an illegal re-usage of
the fileoperations struct if more than one dvb device (e.g. frontend) is
present.

This patch fixes this issue.

It allocates a new fileoperations struct each time a device is
registered and copies the default template fileops.

Signed-off-by: Marcel Siegert <mws@linuxtv.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>