drm: Clarify definition of the DRM_BUS_FLAG_(PIXDATA|SYNC)_* macros

drm: Clarify definition of the DRM_BUS_FLAG_(PIXDATA|SYNC)_* macros

The DRM_BUS_FLAG_PIXDATA_POSEDGE and DRM_BUS_FLAG_PIXDATA_NEGEDGE macros
and their DRM_BUS_FLAG_SYNC_* counterparts define on which pixel clock
edge data and sync signals are driven. They are however used in some
drivers to define on which pixel clock edge data and sync signals are
sampled, which should usually (but not always) be the opposite edge of
the driving edge. This creates confusion.

Create four new macros for both PIXDATA and SYNC that explicitly state
the driving and sampling edge in their name to remove the confusion. The
driving macros are defined as the opposite of the sampling macros to
made code simpler based on the assumption that the driving and sampling
edges are opposite.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>