[media] e4000: various small changes

* Rename device state from 's' to 'dev'.
* Move single include to driver private header.
* Change error handling type of each function to one I tend use
nowadays.
* Remove dummy register write from init. Even Windows driver does this
multiple times remove it as I have never seen any I2C errors.
* Define I2C client pointer for each function and use it.
* Do not clean tuner ops during driver remove - not needed.
* Disable sysfs device bind / unbind. We are not allowed manually
bind / unbind device from the driver currently.
* Rename some other variables.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>