rk3399: display: Use edid_set_framebuffer_bits_per_pixel() helper

This refactoring was already carried into RK3288 with commit 6911219
(edid: Add helper function to calculate bits-per-pixel dependent values)
but it seems that the code for RK3399 was copy&pasted from it too early
to pick this up. Fix that so that future Rockchip SoCs can copy&paste
the right thing.

Change-Id: I5050c58d18db38fffabc7666e67a622d4a828590
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/17050
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/soc/rockchip/rk3399/display.c b/src/soc/rockchip/rk3399/display.c
index d69df93..2679860 100644
--- a/src/soc/rockchip/rk3399/display.c
+++ b/src/soc/rockchip/rk3399/display.c
@@ -95,11 +95,8 @@
 		return;
 	}
 
-	edid.framebuffer_bits_per_pixel = conf->framebuffer_bits_per_pixel;
-	edid.bytes_per_line =
-			edid.mode.ha * conf->framebuffer_bits_per_pixel / 8;
-	edid.x_resolution = edid.mode.ha;
-	edid.y_resolution = edid.mode.va;
+	edid_set_framebuffer_bits_per_pixel(&edid,
+		conf->framebuffer_bits_per_pixel, 0);
 	rkvop_mode_set(conf->vop_id, &edid, detected_mode);
 
 	rkvop_enable(conf->vop_id, lcdbase, &edid);