dt-bindings: i2c: Use correct vendor prefix for Atmel

dt-bindings: i2c: Use correct vendor prefix for Atmel

The "at," prefix was never correct for Atmel, so fix the few occurrences
that got it wrong. Use "atmel," instead.

While at it, remove the at,24c08 compatible string from the list of
trivial devices because it is already documented in eeprom/at24.txt.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>