Add support for the Okaya RS800480T-7X0GP to the DRM simple panel
driver.

The RS800480T-7X0GP is a WVGA (800x480) panel with an 18-bit parallel
LCD interface. It supports pixel clocks in the range of 30-40 MHz.

This panel details can be found at:
http://boundarydevices.com/product/7-800x480-display/Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>