drivers: display: ssd1673: Fixup dts support

There were several issues in the dts binding for the ssd1673 display:
* binding file mixed description & generation up together
* Use of BASE_LABEL
* orientation-flipped should have been of type boolean

Update the binding file to reflect these changes, and made associated
changes to dts_fixup.h and driver as needed.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>