V4L/DVB (4918): Budget-av: Add delay for frontend power-on

Added a delay to give the frontend a little bit time for power-on.

Signed-off-by: Hartmut Birr <e9hack@googlemail.com>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>