drm/pl111: Properly detect the ARM PL110 variants

With a bit of refactoring we can contain the variant data for
the strange PL110 versions that is feature-incomplete PL110 for
the ARM Integrator/CP and somewhere inbetween PL110 and PL111
for the ARM Versatile AB and Versatile PB.

We also accomodate for the custom duct-taped RGB565/BGR565 support
in the Versatile variant.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180206093540.8147-1-linus.walleij@linaro.org

drivers/gpu/drm/pl111/pl111_drm.h

@@ -36,12 +36,15 @@ struct drm_minor;
  * struct pl111_variant_data - encodes IP differences
  * @name: the name of this variant
  * @is_pl110: this is the early PL110 variant
+ * @external_bgr: this is the Versatile Pl110 variant with external
+ *	BGR/RGB routing
  * @formats: array of supported pixel formats on this variant
  * @nformats: the length of the array of supported pixel formats
  */
 struct pl111_variant_data {
 	const char *name;
 	bool is_pl110;
+	bool external_bgr;
 	const u32 *formats;
 	unsigned int nformats;
 };