drm/i2c: adv7511: Move to bridge folder

The driver has been converted to use drm_bridge instead of
drm_i2c_slave_encoder. We can now move it to the bridge folder.

Create a separate folder since we already have a couple of files and
expect more when we support audio and ADV7533.

Rename the driver to adv7511_drv.c. This will come in handy later
when the driver module will need to be built from multiple object
files.

Signed-off-by: Archit Taneja <architt@codeaurora.org>