imx-drm: imx-tve: Fix DDC I2C bus property

This patch fixes the TV Encoder DDC I2C bus property to use the common
'ddc-i2c-bus' property name instead of 'ddc'.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>