V4L/DVB (11743): Analog Devices ADV7343 video encoder driver

Add ADV7343 I2C based video encoder driver. This follows the
v4l2-subdev framework. This driver has been tested on TI DM646x EVM. It
has been tested for Composite and Component outputs.

Updates as per review by Mauro Chehab, added support for more standards
supported by the encoder. Also adding the missed out signed-offs.Tested
only NTSC and PAL standards.

[hverkuil@xs4all.nl: s_routing API changed, updated driver to use new API]
Signed-off-by: Manjunath Hadli <mrh@ti.com>
Signed-off-by: Brijesh Jadav <brijesh.j@ti.com>
Signed-off-by: Chaithrika U S <chaithrika@ti.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>