drm/panel: Add driver for the Toppoly TD028TTEC1 panel

This panel is used on the OpenMoko Neo FreeRunner and Neo 1973.

The code is based on the omapdrm-specific panel-tpo-td028ttec1 driver.

v2:
- fix checkpatch warnings:
  o (lcd == NULL) => (!lcd) (sam)
  o (1 << X) => BIT(X) (sam)

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190813201101.30980-9-laurent.pinchart@ideasonboard.com