media: ngene: add I2C_FUNC_I2C to the I2C interface functionality

Report I2C_FUNC_I2C in .functionality() as well. The I2C interface can
handle this fine and even is required for all I2C client drivers that
utilise the regmap API which are used from within the ngene driver.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Jasmin Jessich <jasmin@anw.at>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>