Platform specific display device setup for DM646x EVM

Add platform device and resource structures. Also define a platform specific
clock setup function that can be accessed by the driver to configure the clock
and CPLD.
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: Kevin Hilman <khilman@deeprootsystems.com>