media: ddbridge: use the ddbridge's own dummy fe driver

Cleanup the ddbridge's dummy driver by removing the parts
that aren't needed by ddbridge, adding it to the building
system and changing the binding at the driver to use the
newer function name.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

media: ddbridge-dummy_fe: do some vars and function renames

As the name of this driver is now ddbridge-dummy, do some
renames internally.

No functional changes.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

media: ddbridge: copy the dvb_dummy_fe driver to ddbridge

As we'll be transforming the dvb-dummy-fe driver soon into a
virtual driver, let's first copy the existing one to ddbridge
as-is, as it is needed there.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>