video: Allow driver to specify the line length

At present line_length is always calculated in video_post_probe(). But
some hardware may use a different line length, e.g. with a 1366-wide
display.

Allow the driver to set this value if needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
diff --git a/drivers/pci/pci_rom.c b/drivers/pci/pci_rom.c
index eaacd40..7d9b75c 100644
--- a/drivers/pci/pci_rom.c
+++ b/drivers/pci/pci_rom.c
@@ -331,6 +331,7 @@
 		return log_msg_ret("No x resolution", -ENXIO);
 	uc_priv->xsize = vesa->x_resolution;
 	uc_priv->ysize = vesa->y_resolution;
+	uc_priv->line_length = vesa->bytes_per_scanline;
 	switch (vesa->bits_per_pixel) {
 	case 32:
 	case 24:
diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
index b6551b6..f307cf2 100644
--- a/drivers/video/video-uclass.c
+++ b/drivers/video/video-uclass.c
@@ -226,7 +226,9 @@
 
 	/* Set up the line and display size */
 	priv->fb = map_sysmem(plat->base, plat->size);
-	priv->line_length = priv->xsize * VNBYTES(priv->bpix);
+	if (!priv->line_length)
+		priv->line_length = priv->xsize * VNBYTES(priv->bpix);
+
 	priv->fb_size = priv->line_length * priv->ysize;
 
 	/* Set up colors  */