Enable 16 bit and 32 bit color depth support in QEMU VGA device driver

Now that our framebuffer code basically supports 16 and 32 bit color depths,
we can also enable support for these resolutions in the QEMU VGA device driver.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>

board-qemu/slof/pci-device_1234_1111.fs

@@ -255,18 +255,18 @@ a CONSTANT VBE_DISPI_INDEX_NB
 ;
 
 : display-install ( -- )
-   is-installed? NOT IF
-      disp-depth 8 = IF
+    is-installed? NOT IF
         ." Installing QEMU fb" cr
         fb-base to frame-buffer-adr
         clear-screen
         default-font 
         set-font
-        disp-width disp-height disp-width char-width / disp-height char-height / ( width height #lines #cols )
-        fb8-install 
+        disp-width disp-height
+        disp-width char-width / disp-height char-height /
+        disp-depth 8 /                      ( width height #lines #cols depth )
+        fb-install
         true to is-installed?
-     THEN
-   THEN
+    THEN
 ;
 
 : dimensions ( -- width height )
@@ -274,14 +274,12 @@ a CONSTANT VBE_DISPI_INDEX_NB
 ;
 
 : set-alias
-  disp-depth 8 = IF
     s" screen" find-alias 0= IF
       \ no previous screen alias defined, define it...
       s" screen" get-node node>path set-alias
     ELSE
        drop
     THEN 
-  THEN
 ;