Add support for depth 15 to qemu_default_pixelformat()

Makes qemu_default_pixelformat(15) return pixelformat filled for 15 bit
color depth (16 bpp, 5 bits for red,green,blue each, 1 bit unused).
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

console.c

@@ -1621,6 +1621,22 @@ PixelFormat qemu_default_pixelformat(int bpp)
     pf.depth = bpp == 32 ? 24 : bpp;
 
     switch (bpp) {
+        case 15:
+            pf.bits_per_pixel = 16;
+            pf.bytes_per_pixel = 2;
+            pf.rmask = 0x00007c00;
+            pf.gmask = 0x000003E0;
+            pf.bmask = 0x0000001F;
+            pf.rmax = 31;
+            pf.gmax = 31;
+            pf.bmax = 31;
+            pf.rshift = 10;
+            pf.gshift = 5;
+            pf.bshift = 0;
+            pf.rbits = 5;
+            pf.gbits = 5;
+            pf.bbits = 5;
+            break;
         case 16:
             pf.rmask = 0x0000F800;
             pf.gmask = 0x000007E0;