Change default visual to have a depth of bitsPerPixel.

This results in the default visual including alpha in the depth.
This is the behavour expected by the xorg render implementation, so appears
to be reasonably standard.

(cherry picked from commit c0bc3fb1f9a1a975c060d6db381498a2e2126a53)
From: git://anongit.freedesktop.org/xorg/driver/xf86-video-armsoc
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>

BUG=chromium:330669
TEST=DISPLAY=:0 xdpyinfo
  depth of root window:    32 planes
  ...
  number of visuals:    2
  default visual id:  0x21
  visual:
    visual id:    0x21
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x22
    class:    DirectColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits

Change-Id: Iacb8a2bf0689c90c9ab3767087d54752779090e5
Reviewed-on: https://chromium-review.googlesource.com/183605
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>
Commit-Queue: Daniel Kurtz <djkurtz@chromium.org>
diff --git a/src/omap_driver.c b/src/omap_driver.c
index 8430e2c..f91c2a1 100644
--- a/src/omap_driver.c
+++ b/src/omap_driver.c
@@ -591,7 +591,7 @@
 	 */
 
 	miClearVisualTypes();
-	if (!miSetVisualTypes(pScrn->depth, miGetDefaultVisualMask(pScrn->depth),
+	if (!miSetVisualTypes(pScrn->bitsPerPixel, miGetDefaultVisualMask(pScrn->depth),
 			pScrn->rgbBits, pScrn->defaultVisual)) {
 		ERROR_MSG("Cannot initialize the visual type for %d bits per pixel!",
 				pScrn->bitsPerPixel);