qemu: fix PPC not working with 256 colours

Thanks @cat7 for suggesting the patch.

Fixes #4277

patches/qemu-7.0.0-utm.patch

@@ -466,3 +466,131 @@ index 8692ea2561..5ee2cc88d5 100644
 -- 
 2.28.0
 
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+Subject: [PATCH] ui/console: fix qemu_console_resize() regression
+Date: Mon, 25 Jul 2022 15:58:15 +0400
+Message-Id: <20220725115815.2461322-1-marcandre.lureau@redhat.com>
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+From: Marc-André Lureau <marcandre.lureau@redhat.com>
+
+The display may be corrupted when changing screen colour depth in
+qemu-system-ppc/MacOS since 7.0.
+
+Do not short-cut qemu_console_resize() if the surface is backed by vga
+vram. When the scanout isn't set, or it is already allocated, or opengl,
+and the size is fitting, we still avoid the reallocation & replace path.
+
+Fixes: commit cb8962c1 ("ui: do not create a surface when resizing a GL scanout")
+
+Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
+Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
+Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
+Acked-by: Gerd Hoffmann <kraxel@redhat.com>
+---
+ ui/console.c | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/ui/console.c b/ui/console.c
+index e139f7115e1f..765892f84f1c 100644
+--- a/ui/console.c
++++ b/ui/console.c
+@@ -2575,11 +2575,13 @@ static void vc_chr_open(Chardev *chr,
+ 
+ void qemu_console_resize(QemuConsole *s, int width, int height)
+ {
+-    DisplaySurface *surface;
++    DisplaySurface *surface = qemu_console_surface(s);
+ 
+     assert(s->console_type == GRAPHIC_CONSOLE);
+ 
+-    if (qemu_console_get_width(s, -1) == width &&
++    if ((s->scanout.kind != SCANOUT_SURFACE ||
++         (surface && surface->flags & QEMU_ALLOCATED_FLAG)) &&
++        qemu_console_get_width(s, -1) == width &&
+         qemu_console_get_height(s, -1) == height) {
+         return;
+     }