i2c: at91: add support for analog filtering

Add support for analog filtering for i2c lines.
The sama5d2 and sam9x60 support this feature.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>